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I've been tasked at work to write a detailed engineering plan for a logistics application that we are coding to propose to a customer. I have been told that it is a data-driven application. What does it mean for an application to be "data-driven"? What is the opposite? I can't seem to get any really clear answer for this although while web searching I can see many people posting their own examples. Any help would be greatly appreciated.
Data driven progamming is a programming model where the data itself controls the flow of the program and not the program logic. It is a model where you control the flow by offering different data sets to the program where the program logic is some generic form of flow or of state-changes.
For example if you have program that has four states: UP - DOWN - STOP - START
You can control this program by offering input (data) that represents the states:
set1: DOWN - STOP - START - STOP - UP - STOP
set2: UP - DOWN - UP - DOWN
The program code stays the same but data set (which is not of a dynamic input type but statically given to the computer) controls the flow.
Although there are more than a few ideas as to what data driven programming is, allow me to give an example using a data structure and a function.
Non data driven example:
data_lloyd = {'name': 'Lloyd', 'lives': 'Alcoy }
data_jason = {'name': 'Jason', 'lives': 'London' }
go = function(x)
if x.name == 'Lloyd'
then
print("Alcoy, Spain")
else
print("London, UK")
end
Data driven example:
data_lloyd = {'name': 'Lloyd', 'lives': function(){ print("Alcoy, Spain") }
data_jason = {'name': 'Jason', 'lives': function(){ print("London, UK") }
go = function(x)
x.lives()
end
In the first example the decision to show one result or the other is in the code logic.
In the last example the output is determined by the data that is passed to the function and for that reason we say the output is 'driven' by the data.
"I have been told that it is a data-driven application" - you need to ask whoever told you that.
You don't want to read some plausible answer here and then find out that it's not at all what the person in charge of your project meant. The phrase is too vague to have an unambiguous meaning that will definitely apply to your project.
Data driven development is something that one can make changes to the
logic of the program by editing not the code but the data structure.
You might find more information about data-driven programming here.
Procedural Programming
var data = {
{do:'add',arg:{1,2}},
{do:'subtract',arg:{3,2}},
{do:'multiply',arg:{5,7}},
};
foreach(var item in data){
switch(item.do){
case 'add':
console.log(item.arg[0] + item.arg[1]);
break;
case 'subtract':
console.log(item.arg[0] - item.arg[1]);
break;
case 'multiply':
console.log(item.arg[0] * item.arg[1]);
break;
}
}
Data Driven Programming
var data = {
{do:'+',arg:{1,2}},
{do:'-',arg:{3,2}},
{do:'*',arg:{5,7}},
};
foreach(var item in data){
console.log(eval (item.arg[0] + item.do + item.arg[1]);
}
Data driven application is:
(1) a set of rules accepting different data sets to make a predetermined decision for each specific data set and throwing outcome as result
(2) a few predetermined processes that are triggered based on the outcome.
Perfect example is ifttt.com
The application has nothing but rules.
What makes it useful is the data that will flow through it.
This article explains most clearly what I understand the term to mean:
What is Table-Driven and Data-Driven Programming?
http://www.paragoncorporation.com/ArticleDetail.aspx?ArticleID=31
Data/Table-Driven programming is the
technique of factoring repetitious
programming constructs into data and a
transformation pattern. This new data
is often referred to by purists as
meta-data when used in this fashion.
There is no one at work that can help you with this question? It is very hard to visualize what you are working without without a greater example. But from what I gather it is going to be a program that they primarily enter information into. That will be able to retrieve and edit information that the customer needs to manage.
Best of luck!!
I think the advice given isn't bad, but I've always thought of Data Driven Design revolves around using existing or given data structures as the foundation for your domain objects.
For instance, the classic salesperson management program might have the following type structure of tables:
Salesperson
Region
Customers
Products
So, your application would be centered around managing these data structures, instead of taking a straight API which does things like - "make sale" etc...
Just my opinion as the other answers suggest ;)
Imagine you need a program that prompts the user for nouns and adjectives (or other language constructs) which you will use to fill in a sentence (e.g. MadLibs).
Procedural example
noun1 = input('Noun: ')
noun2 = input('Noun: ')
adj = input('Adjective: ')
print(f'The {noun1} jumped over the {adj} {noun2}')
If you wanted to write a different version (more nouns, different phrase, etc.) you would write a different program.
Data-driven example
def get_inputs(inputs_needed):
inputs = {}
for key, prompt in inputs_needed.items():
inputs[key] = input(prompt + ': ')
return inputs
for game in games_json:
inputs = get_inputs(game['inputs_needed'])
print(game['phrase'].format(**inputs)
Now an individual game can be defined as:
{
"inputs_needed": {
"noun1": "Noun",
"noun2": "Noun",
"adj": "Adjective"
},
"phrase": "The {noun1} jumped over the {adj} {noun2}"
}
Now to create a new version, you simply change the JSON. The code stays the same.
I have objects called Country. At some point in the program, I want to set the field power of each object.
The power for each country is fixed and I have data for all 196 countries here on a piece of paper. My code should check, for instance, if the country's name is USA (and if so, set its power to 100) and so on.
I know I can do it with a switch-case, but what is the best, nicest, and most efficient way to do it?
You can store country-power pairs into a Dictionary<string, int> then just get the score of a particular country by using indexer:
var points = new Dictionary<string,int>();
// populate the dictionary...
var usa = points["USA"];
Edit: As suggested in comments you should store the information in external file, for example an xml would be a good choice. That way you don't have to modify the code to add or remove countries. You just need to store them into XML file, edit it whenever you need.Then parse it when your program starts, and load the values into Dictionary.You can use LINQ to XML for that.If you haven't use it before there are good examples in the documentation to get you started.
Whilst Selmans answer is right and good, it does not answer how to actually populate the Dictionary. Here is it:
var map = new Dictionary<string, int> {
{"USA", 100},
{"Germany", 110}
};
you may however also just add it as follows:
map.Add("USA", 100);
map.Add("Germany", 110);
Now you may access the value (as already mentioned by Semans):
map["USA"] = 50; // set new value for USA
int power = map["USA"]; // get new value
EDIT: As already mentioned within comments and other answers you may of course store the data within an external file or any other data-storage. Having said this you may just initialize an empty dictionary and then fill it with the Add-method previously mentioned for every record within that storage.
This is the right question to begin with, but there are a lot of things you need to learn. Many folk have given you answers to the question you asked. I'm going to be annoyingly Zen and tell you to unask the question because there is a larger problem to resolve.
Instead of hard coding this, store the related properties in an n-tuple also known as a database row and use a database engine to manage the relation between the two. And then since you are using C# it would probably be smart to learn to use LINQ. But before you do that, learn a bit of data modelling theory, because data-modelling is what you are doing.
Since you said you have "objects" called "Country", and you have tagged your question "C#", it would seem that you have two forces at work in your code. One is that having to refer to a map, however efficiently implemented, is not as cheap as referring to a member variable. On the other hand there might be some benefit to a setup where all the attributes of a country can be found in the same place as the attributes of other countries (the map-oriented solutions do address this concern). But these forces can be reconciled something like this:
class Country { // Apologies that this sketch is more C++ than C#
public:
Country(string name_, int power_);
private:
string name;
int power;
};
void MakeCountries()
{
countries.Add(new Country("USA", 50));
countries.Add(new Country("Germany", 60));
// ....
}
Do you need to update your data at runtime?
Yes? Load data from external storage into a dictionary.
No? Use a switch
Let the compiler generate dictionaries and hash-based lookups for you.
When you profiler starts screaming, explore alternative solutions.
For example, read that answer from "What is quicker, switch on string or elseif on type?".
What about making an array of Strings for storing country names in ascending order of their power. It will be more simple to implement.Then the index of each country can represent its power. This is possible, only if the power is continues counting numbers.
If its not , another siple way is to implement them as linked list. So that u will be able to change if u want. A list with 2 fields; 1for the country and other for the power
I'm working on a new project.
My best analogy would be a psychological evaluation test maker.
Aspect #1.
The end-business-user needs to create test questions. With question types. And possible responses to the questions when applicable.
Examples:
1. Do you have red hair? (T/F)
2. What is your favorite color? (Single Response/Multiple Choice)
(Possible Responses: Red, Yellow, Black, White)
3. What size shoe do you wear (rounded to next highest size)? (Integer)
4. How much money do you have on you right now? (Dollar Amount (decimal))
So I need to be able to create questions, their question type, and for some of the questions, possible answers.
Here:
Number 1 is a know type of "True or False".
Number 2 is a know type of "Single Response/Multiple Choice" AND the end-business-user will create the possible responses.
Number 3 is a known type of "Integer". The end-user (person taking the evaluation) can basically put in any integer value.
Number 4 is a known type of "Decimal". Same thing as Integer.
Aspect #2.
The end-business-user needs to evaluate the person's responses. And assign some scalar value to a set of responses.
Example:
If someone responded:
1. T
2. Red
3. >=8
4. (Not considered for this situation)
Some psychiatrist-expert figures out that if someone answered with the above responses, that you are a 85% more at risk for depression than the normal. (Where 85% is a number the end-business-user (psychiatrist) can enter as a parameter.
So Aspect #2 is running through someone's responses, and determining a result.
The "response grid" would have to be setup so that it will go through (some or all) the possibilities in a priority ranking order, and then after all conditions are met (on a single row), exit out with the result.
Like this:
(1.) T (2.) Red (3.) >=8 ... Result = 85%
(1.) T (2.) Yellow (3.) >=8 ... Result = 70%
(1.) F (2.) Red (3.) >=8 ... Result = 50%
(1.) F (2.) Yellow (3.) >=8 ... Result = 40%
Once a match is found, you exit with the percentage. If you don't find a match, you go to the next rule.
Also, running with this psych evaluation mock example, I don't need to define every permutation. A lot of questions of psych evaluations are not actually used, they are just "fluff". So in my grid above, I have purposely left out question #4. It has no bearing on the results.
There can also be a "Did this person take this seriously?" evaluation grid:
(3.) >=20 (4.) >=$1,000 ... Result = False
(The possibility of having a shoe size >= 20 and having big dollars in your pocket is very low, thus you probably did not take the psych test seriously.)
If no rule is found, (in my real application, not this mock up), I would throw an exception or just not care. I would not need a default or fall-through rule.
In the above, Red and Yellow are "worrisome" favorite colors. If your favorite color is black or white, it has no bearing upon your depression risk factor.
I have used Business Rule Engines in the past. (InRule for example).
They are very expensive, and it is not in the budget.
BizTalk Business Rules Framework is a possibility. Not de$irable, but possible.
My issue with any Rules-Engine is that the "vocabulary" (I have limited experience with business rules engines, mind you) is based off of objects, with static properties.
public class Employee
{
public string LastName
{ get; set; }
public DateTime HireDate
{ get; set; }
public decimal AnnualSalary
{ get; set; }
public void AdjustSalary(int percentage)
{
this.AdjustSalary= this.AdjustSalary + (this.AdjustSalary * percentage);
}
}
This would be easy to create business rules.
If
the (Employee's HireDate) is before (10 years ago)
then
(Increase Their Salary) By (5) Percent.)
else
(Increase Their Salary) By (3) Percent.)
But in my situation, the Test is composed of (dynamic) Questions and (dynamic) Responses, not predetermined properties.
So I guess I'm looking for some ideas to investigate on how to pull this off.
I know I can build a "TestMaker" application fairly quickly.
The biggest issue is integrating the Questions and (Possible Responses) into "evaluating rules".
Thanks for any tips.
Technologies:
DotNet 4.0 Framework
Sql Server 2008 Backend Database
VS2010 Pro, C#
If it's a small application, i.e 10s of users as opposed to 1000s, and its not business critical, then I would recommend Excel.
The advantages are, most business users are very familiar with excel and most probably have it on their machines. Basically you ship an Excel Workbook to your business users. They would enter the questions, the Type (Decimal, True False etc.). Click a button which triggers an excel macro. This could generate an XML configuration file or put the questions into SQL. Your application just reads it, displays it and collects responses as usual.
The main advantage of Excel comes in Aspect #2, the dynamic user chosen business rules. In another sheet of the same Excel document, the end business user can specify as many of the permutations of the responses/questions as they feel like. Excel users are very familiar with inputting simple formulas like =If(A1 > 20 && A2 <50) etc. Again the user pushes a button and generates either a configuration file or input the data into SQL server.
In your application you iterate through the Rules table and apply it to the responses.
Given the number of users/surveys etc. This simple solution would be much more simpler than biztalk or a full on customs rules engine. Biztalk would be good if you need to talk to multiple system, integrate their data, enforce rules, create work flow etc. Most of the other rules engines are also geared towards really big, complex rule system. The complexity in this rule systems, isn't just the number of rules or permutations, it is mostly having to talk to multiple system or "End dating" certain rules or putting in rules for future kick off dates etc.
In your case an Excel based or a similar datagrid on a webpage system would work fine. Unless of course you are doing a project for Gartner or some other global data survey firm or a major government statistical organisation. In that case I would suggest Biztalk or other commercial rules engines.
In your case, its SQL tables with Questions, Answer Types, Rules To Apply. Input is made user friendly via Excel or "Excel in the web" via a datagrid and then just iterate through the rules and apply them to the response table.
Are you sure you want to use a business rule engine for this problem?
As far as I understand it, the usecase for a BRE is
Mostly static execution flow
Some decisions do change often
In your usecase, the whole system (Q/A-flow and evaluation) are dynamic, so IMHO a simple domain specific language for the whole system would be a better solution.
You might want to take some inspiration from testMaker - a web based software exactly for this workflow. (Disclaimer: I contributed a bit to this project.) Its scoring rules are quite basic, so this might not help you that much. It was designed to export data to SPSS and build reports from there...
Be sure you are modeling a database suitable for hierarchical objects This article would help
create table for test
create tables for questions, with columns question, testid, questiontype
create tables for answers, answer id,question id, answer and istrue columns
answers belong to questions
one question can have many answer
create table for user or employee
create table for user answers, answer id, selected answer
evaluation (use object variables for boolean-integer coverage, use try catch before using function for high exception coverage.):
function(questiontype,answer,useranswer)
switch(questiontype) //condition can be truefalse, biggerthan,smallerthan, equals
{
case: "biggerthan": if(useranswer>answer) return true else return false;
case "truefalse": if(useranswer==answer) return true else return false
case "equals": if(useranswer==answer) return true else return false
}
get output as a data dictionary and post here please.
without a data schema the help you get will be limited.
Many times, when generating messages to show to the user, the message will contain a number of something that I want to inform the customer about.
I'll give an example: The customer has selected a number of items from 1 and up, and has clicked delete. Now I want to give a confirmation message to the customer, and I want to mention the number of items he has selected to minimize the chance of him making a mistake by selecting a bunch of items and clicking delete when he only wants to delete one of them.
One way is to make the generic message like this:
int noofitemsselected = SomeFunction();
string message = "You have selected " + noofitemsselected + " item(s). Are you sure you want to delete it/them?";
The "problem" here is the case where noofitemselected is 1, and we have to write item and it instead of items and them.
My normal solution will be something like this
int noofitemsselected = SomeFunction();
string message = "You have selected " + noofitemsselected + " " + (noofitemsselected==1?"item" : "items") + ". Are you sure you want to delete " + (noofitemsselected==1?"it" : "them") + "?";
This gets quite long and quite nasty really fast if there are many references to the numbers plurality inside the code, and the actual message gets hard to read.
So my questions is simply. Are there any better ways of generating messages like this?
EDIT
I see a lot of persons has got very hung up in the case that I mentioned that the message should be displayed inside a message box, and has simply given an answer of how to avoid using the message box at all, and that is all good.
But remember that the problem of pluralization also apply to texts other places in the program in addition to message boxes. For example, a label alongside a grid displaying the number of lines selected in the grid will have the same problem regarding pluralization.
So this basically apply to most text that is outputted in some way from programs, and then the solution is not as simple as to just change the program to not output text anymore :)
You can avoid all of this messy plurality by just deleting the items without any message and giving the user a really good Undo facility. Users never read anything. You should build a good Undo facility as part of your program anyway.
You actually get 2 benefits when you createe a comprehensive Undo facility. The first benefit makes the user's life easier by allowing him/her to reverse mistakes and minimise reading. The second benefit is that your app is reflecting real life by allowing the reversal of non-trivial workflow (not just mistakes).
I once wrote an app without using a single dialog or confirmation message. It took some serious thinking and was significantly harder to implement than using confirmation-type messages. But the end result was rather nice to use according to its end-users.
If there is ever any chance, no matter how small, that this app will need to be translated to other languages then both are wrong. The correct way of doing this is:
string message = ( noofitemsselected==1 ?
"You have selected " + noofitemsselected + " item. Are you sure you want to delete it?":
"You have selected " + noofitemsselected + " items. Are you sure you want to delete them?"
);
This is because different languages handle plurality differently. Some like Malay don't even have syntactic plurals so the strings would generally be identical. Separating the two strings makes it easier to support other languages later on.
Otherwise if this app is meant to be consumed by the general public and is supposed to be user friendly then the second method is preferable. Sorry but I don't really know a shorter way of doing this.
If this app is meant to be consumed only internally by your company then do the shortcut "item(s)" thing. You don't really have to impress anybody when writing enterprisy code. But I'd advise against doing this for publicly consumed app because this gives the impression that the programmer is lazy and thus lower their opinion of the quality of the app. Trust me, small things like this matter.
How about just:
string message = "Are you sure you want to delete " + noofitemsselected + " item(s)?"
That way, you eliminate the number agreement difficulties, and end up with an even shorter, more to-the-point error message for the user as a bonus. We all know users don't read error messages anyway. The shorter they are, the more likely they are to at least glance at the text.
Or, armed with this knowledge that users don't read error messages, you could approach this a different way. Skip the confirmation message altogether, and just provide an undo feature that Just Works, regardless of what was deleted. Most users are already accustomed to undoing an operation when they notice it was not what they wanted, and are likely to find this behavior more natural than having to deal with another annoying pop-up.
What about what Java has had for years: java.text.MessageFormat and ChoiceFormat? See http://download.oracle.com/javase/1.4.2/docs/api/java/text/MessageFormat.html for more information.
MessageFormat form = new MessageFormat("The disk \"{1}\" contains {0}.");
form.applyPattern(
"There {0,choice,0#are no files|1#is one file|1<are {0,number,integer} files}.");
Object[] testArgs = {new Long(12373), "MyDisk"};
System.out.println(form.format(testArgs));
// output, with different testArgs
output: The disk "MyDisk" are no files.
output: The disk "MyDisk" is one file.
output: The disk "MyDisk" are 1,273 files.
In your case you want something somewhat simpler:
MessageFormat form = new MessageFormat("Are you sure you want to delete {0,choice,1#one item,1<{0,number.integer} files}?");
The advantage of this approach is that it works well with the i18n bundles, and you can provide translations properly for languages (like Japanese) that have no concept of plural or singular words.
I'd go with not hardcoding the message, but providing two messages in an seperate Resource file. Like
string DELETE_SINGLE = "You have selected {0} item. Are you sure you want to delete it?";
string DELETE_MULTI = "You have selected {0} items. Are you sure you want to delete them?";
and then feeding them into String.Format like
if(noofitemsselected == 1)
messageTemplate = MessageResources.DELETE_SINGLE;
else
messageTemplate = MessageResources.DELETE_MULTI;
string message = String.Format(messageTemplate, noofitemsselected)
I think that this approach is easier to localize and maintain. All UI messages would be at a single locaion.
You can sidestep the issue entirely by phrasing the message differently.
string message = "The number of selected items is " + noofitemsselected + ". Are you sure you want to delete everything in this selection?";
The first thing I'd suggest is: use string.Format. That allows you to do something like this:
int numOfItems = GetNumOfItems();
string msgTemplate;
msgTemplate = numOfItems == 1 ? "You selected only {0} item." : "Wow, you selected {0} items!";
string msg = string.Format(msgTemplate, numOfItems);
Further, in WPF apps, I've seen systems where a resource string would be pipe-delimited to have two messages: a singular and a plural message (or a zero/single/many message, even). A custom converter could then be used to parse this resource and use the relevant (formatted) string, so your Xaml is something like this:
<TextBlock Text="{Binding numOfItems, Converter={StaticResource c:NumericMessageFormatter}, ConverterParameter={StaticResource s:SuitableMessageTemplate}}" />
For English, plenty of answers above. For other languages it is more difficult, as plurals depend on the gender of the noun and the word ending. Some examples in French:
Regular masculine:
Vous avez choisi 1 compte. Voulez-vous vraiment le supprimer.
Vous avez choisi 2 comptes. Voulez-vous vraiment les supprimer.
Regular feminine
Vous avez choisi 1 table. Voulez-vous vraiment la supprimer.
Vous avez choisi 2 tables. Voulez-vous vraiment les supprimer.
Irregular masculine (finishes with 's')
Vous avez choisi 1 pays. Voulez-vous vraiment le supprimer.
Vous avez choisi 2 pays. Voulez-vous vraiment les supprimer?
The same problem exists in most Latin languages and gets worse in German or Russian, where there are 3 genders (maculine, feminine and neuter).
You'll need to take care if your objective is to handle more than just English.
To be able to have pluralized messages which will be possible to localize properly, my opinion is that it would be wise to first create a layer of indirection between the number and a message.
For example, use a constant of some sort to specify which message you want to display. Fetch the message using some function that will hide the implementation details.
get_message(DELETE_WARNING, quantity)
Next, create a dictionary that holds the possible messages and variations, and make variations know when they should be used.
DELETE_WARNING = {
1: 'Are you sure you want to delete %s item',
>1: 'Are you sure you want to delete %s items'
>5: 'My language has special plural above five, do you wish to delete it?'
}
Now you could simply find the key that corresponds to the quantity and interpolate the value of the quantity with that message.
This oversimplified and naive example, but I don't really see any other sane way to do this and be able to provide good support for L10N and I18N.
You'll have to translate the function below from VBA to C#, but your usage would change to:
int noofitemsselected = SomeFunction();
string message = Pluralize("You have selected # item[s]. Are you sure you want to delete [it/them]?", noofitemsselected);
I have a VBA function that I use in MS Access to do exactly what you are talking about. I know I'll get hacked to pieces for posting VBA, but here goes anyway. The algorithm should be apparent from the comments:
'---------------------------------------------------------------------------------------'
' Procedure : Pluralize'
' Purpose : Formats an English phrase to make verbs agree in number.'
' Usage : Msg = "There [is/are] # record[s]. [It/They] consist[s/] of # part[y/ies] each."'
' Pluralize(Msg, 1) --> "There is 1 record. It consists of 1 party each."'
' Pluralize(Msg, 6) --> "There are 6 records. They consist of 6 parties each."'
'---------------------------------------------------------------------------------------'
''
Function Pluralize(Text As String, Num As Variant, Optional NumToken As String = "#")
Const OpeningBracket = "\["
Const ClosingBracket = "\]"
Const DividingSlash = "/"
Const CharGroup = "([^\]]*)" 'Group of 0 or more characters not equal to closing bracket'
Dim IsPlural As Boolean, Msg As String, Pattern As String
On Error GoTo Err_Pluralize
If IsNumeric(Num) Then
IsPlural = (Num <> 1)
End If
Msg = Text
'Replace the number token with the actual number'
Msg = Replace(Msg, NumToken, Num)
'Replace [y/ies] style references'
Pattern = OpeningBracket & CharGroup & DividingSlash & CharGroup & ClosingBracket
Msg = RegExReplace(Pattern, Msg, "$" & IIf(IsPlural, 2, 1))
'Replace [s] style references'
Pattern = OpeningBracket & CharGroup & ClosingBracket
Msg = RegExReplace(Pattern, Msg, IIf(IsPlural, "$1", ""))
'Return the modified message'
Pluralize = Msg
End Function
Function RegExReplace(SearchPattern As String, _
TextToSearch As String, _
ReplacePattern As String) As String
Dim RE As Object
Set RE = CreateObject("vbscript.regexp")
With RE
.MultiLine = False
.Global = True
.IgnoreCase = False
.Pattern = SearchPattern
End With
RegExReplace = RE.Replace(TextToSearch, ReplacePattern)
End Function
The usage got cut off a bit in the code comments above, so I'll repeat it here:
Msg = "There [is/are] # record[s]. [It/They] consist[s/] of # part[y/ies] each."
Pluralize(Msg, 1) --> "There is 1 record. It consists of 1 party each."
Pluralize(Msg, 6) --> "There are 6 records. They consist of 6 parties each."
Yes, this solution ignores languages that are not English. Whether that matters depends on your requirements.
You could generate the plural automatically, see eg. plural generator.
For plural generating rules see wikipedia
string msg = "Do you want to delete " + numItems + GetPlural(" item", numItems) + "?";
How about a more generic way. Avoid pluralization in the second sentence:
Number of selected items to be deleted: noofitemsselected.
Are you sure?
I find out that doing it this way puts the number at the end of the line which is really easy to spot. This solution would work with the same logic in any language.
My general approach is to write a "single/plural function", like this:
public static string noun(int n, string single, string plural)
{
if (n==1)
return single;
else
return plural;
}
Then in the body of the message I call this function:
string message="Congratulations! You have won "+n+" "+noun(n, "foobar", "foobars")+"!";
This isn't a whole lot better, but at least it, (a) puts the decision in a function and so unclutters the code a little, and (b) is flexible enough to handle irregular plurals. i.e. it's easy enough to say noun(n, "child", "children") and the like.
Of course this only works for English, but the concept is readily extensible to languages with more complex endings.
It occurs to me that you could make the last parameter optional for the easy case:
public static string noun(int n, string single, string plural=null)
{
if (n==1)
return single;
else if (plural==null)
return single+"s";
else
return plural;
}
Internationalization
I assume you want internationalization support, in which case different languages have different patterns for plurals (e.g. a special plural form for 2 of something, or more complicated languages like Polish), and you can't rely on applying some simple pattern to your string to fix it.
You can use GNU Gettext's ngettext function and provide two English messages in your source code. Gettext will provide the infrastructure to choose from other (potentially more) messages when translated into other languages. See http://www.gnu.org/software/hello/manual/gettext/Plural-forms.html for a full description of GNU gettext's plural support.
GNU Gettext is under the LGPL. ngettext is named GettextResourceManager.GetPluralString in the C# port of Gettext.
(If you don't need localization support, and don't want to use Gettext right away, then write your own function that does this for English, and pass two full messages to it, that way if you need l10n later, you can add by rewriting a single function.)
How about to write function like
string GetOutputMessage(int count, string oneItemMsg, string multiItemMsg)
{
return string.Format("{0} {1}", count, count > 1 ? multiItemMsg : oneItemMsg);
}
.. and use it whenever you need?
string message = "You have selected " + GetOutputMessage(noofitemsselected,"item","items") + ". Are you sure you want to delete it/them?";
For the first problem , I mean Pluralize, you can use Inflector.
And for the second, you can use a string representation extension with a name such as ToPronounString.
I had this exact same question posed to me yesterday by a member of our team.
Since it came up again here on StackOverflow I figured the universe was telling me to have a bash at producing a decent solution.
I've quickly put something together and it's by no means perfect however it might be of use or spark some discussion/development.
This code is based on the idea that there can be 3 messages. One for zero items, one for one item and one for more than one item which follow the following structure:
singlePropertyName
singlePropertyName_Zero
singlePropertyName_Plural
I've created an internal class to test with in order to mimick the resource class. I haven't tested this using an actual resource file yet so I'm yet to see the full result.
Here's the code (currently i've included some generics where I know I could have specified the third param simply as a Type and also the second param is a string, I think there's a way to combine these two parameters into something better but I'll come back to that when I have a spare moment.
public static string GetMessage<T>(int count, string resourceSingularName, T resourceType) where T : Type
{
var resourcePluralName = resourceSingularName + "_Plural";
var resourceZeroName = resourceSingularName + "_Zero";
string resource = string.Empty;
if(count == 0)
{
resource = resourceZeroName;
}
else{
resource = (count <= 1)? resourceSingularName : resourcePluralName;
}
var x = resourceType.GetProperty(resource).GetValue(Activator.CreateInstance(resourceType),null);
return x.ToString();
}
Test resource class:
internal class TestMessenger
{
public string Tester{get{
return "Hello World of one";}}
public string Tester_Zero{get{
return "Hello no world";}}
public string Tester_Plural{get{
return "Hello Worlds";}}
}
and my quick executing method
void Main()
{
var message = GetMessage(56, "Tester",typeof(TestMessenger));
message.Dump();
}
From my point of view, your first solution is the most suited one. Why I say that is, in case you need the application to support multiple languages, the second option can be painstaking. With the fist approach it is easy to localize the text without much effort.
You could go for a more generic message like 'Are you sure you want to delete the selected item(s)'.
I depends on how nice a message you want to have. From easiest to hardest:
Re-write your error message to avoid pluralization. Not as nice for your user, but faster.
Use more general language but still include the number(s).
Use a "pluralization" and inflector system ala Rails, so you can say pluralize(5,'bunch') and get 5 bunches. Rails has a good pattern for this.
For internationalization, you need to look at what Java provides. That will support a wide variety of languages, including those that have different forms of adjectives with 2 or 3 items. The "s" solution is very English centric.
Which option you go with depends on your product goals. - ndp
Why would you want to present a message the users can actually understand? It goes against 40 years of programing history. Nooooo, we have a good thing going on, don't spoil it with understandable messages.
(j/k)
Do it like it's done in World of Warcraft:
BILLING_NAG_WARNING = "Your play time expires in %d |4minute:minutes;";
It gets a little bit shorter with
string message = "Are you sure you want to delete " + noofitemsselected + " item" + (noofitemsselected>1 ? "s" : "") + "?";
One approach I haven't seen mentioned would be the use of a substitution/select tag (e.g. something like "You are about to squash {0} [?i({0}=1):/cactus/cacti/]". (in other words, have a format-like expression specify the substitution based upon whether argument zero, taken as an integer, equals 1). I've seen such tags used in the days before .net; I'm not aware of any standard for them in .net, nor do I know the best way to format them.
I would think out of the box for a minute, all of the suggestions here are either do the pluralization (and worry about more than 1 level of pluralization, gender, etc) or not use it at all and provide a nice undo.
I would go the non lingual way and use visual queues for that. e.g. imagine an Iphone app you select items by wiping your finger. before deleting them using the master delete button, it will "shake" the selected items and show you a question mark titled box with a V (ok) or X (cancel) buttons...
Or, in the 3D world of Kinekt / Move / Wii - imagine selecting the files, moving your hand to the delete button and be told to move your hand above your head to confirm (using the same visual symbols as I mentioned before. e.g. instead of asking you delete 3 files? it will show you 3 files with a hovering half transparent red X on and tell you to do something to confirm.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
What are ‘closures’ in .NET?
I am currently looking at lambda expression and the word closure keeps coming. Can someone explain it to me in real simple language.
I'd say this is a duplicate of: What are ‘closures’ in .NET?
"In essence, a closure is a block of code which can be executed at a later time, but which maintains the environment in which it was first created - i.e. it can still use the local variables etc of the method which created it, even after that method has finished executing."
Your shoes are in the hall; your
jacket is in the kitchen. Put them
on, and your gloves (they're in the
drawer), when going outside.
Now you can go playing with your cars.
At eleven o'clock you must go buy some
bread in the corner store.
Kid plays. Forgets all the world.
Alarm clock goes off; kid sees: eleven o'clock! Oh - go outside to buy bread using the "going outside" closure.
I like the Google example for Javascript (you can morph it for C# easily). It's not something a 5 year old would understand but then I doubt an average 5 year old would understand what a function was.
/*
* When a function is defined in another function and it
* has access to the outer function's context even after
* the outer function returns
* An important concept to learn in Javascript
*/
function outerFunction(someNum) {
var someString = 'Hai!';
var content = document.getElementById('content');
function innerFunction() {
content.innerHTML = someNum + ': ' + someString;
content = null; // IE memory leak for DOM reference
}
innerFunction();
}
The below answer was to the original wording which was akin to "How to explain closures to a 5-year old."
Take this box of legos; build yourself
a nice little space craft. When you go
to billy's house and bring your space
craft there; with closures you can
still can use all the pieces in your
box of legos, even though the box was left
in your bedroom.
If you really need to keep it simple, then a closure is a function with its context. The function in the closure can still access the same variables it could when it was defined, no matter where you call it from. (In Lua, these are called upvalues, which I think is a very descriptive term.)
I met the concept first in Lua, and this definition helped me understand the concept. Maybe have a look at Lua: its simpleness and power is fascinating, and certainly helps to develop a certain view at other languages. Its concept of closures would be a good example to that.
If the 5 year old knew C#, I would explain with this code sample:
int i = 0;
string result = null;
Action iExaminer = () =>
{
result = i % 2 == 1 ? "Odd" : "Even";
};
i = 1;
iExaminer();
Console.WriteLine(result);
If the 5 year old was learning linq, I would explain with this code sample:
string name = null;
IEnumerable<Customer> query = Customers.Where(c => c.Name == name);
name = "Bob";
// query is resolved when enumerated (which is now)
// Where will now call our anonymous method.
foreach(var customer in query)
{
Console.WriteLine(customer.Name);
}
Closure (computer science) says:
In computer science, a closure is a first-class function with free variables that are bound in the lexical environment.
Translation:
Closures close/attach the variables around the function, so that that function can be teleported to somewhere else and still use those variables
e.g. suppose you are teleported to a remote location but have still access to your coffed mug lying on your table
Example:
function makefunc(x)
{
return function(){return x}
}
Now using makefunc, you can make many anonymous functions which will return what you pass to makefunc
So if you want a function which returns 10, use makefunc(10)(), though pretty useless way toget back 10 :)
When you know how to do something in general, you can specify some (or all) details and get a closure.
For example, you know how to buy ice-cream. Yyou know what to do if you will be in front of any shop. But if you want to go to a particular shop (for example, due to a Sunday discount), you move out of house with the aim of buying ice-cream there. "Buy some ice-cream at a store on the corner" is a closure of "buy some ice-cream". In fact, all these are closures of "buy some ice-cream somewhere":
Buy some ice-cream at the corner
Buy two ice-creams
Buy two ice-creams at the corner
Now go play with your friends, son! (and I bear in mind not say anything like that in front of the children)
This is a simple approach to the idea in C#: Closure