Support object literals or anonymous classes

[DartBot]

This issue was originally filed by [email protected]

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In JavaScript Partial Application and Currying is wellknown. Things like this are possible:

{{{code}}}
numberGame() {
   var secretNumber = 21;

   return () {
       guess(g) {
               if(g == secretNumber) {
                       return "Correct";
               } else {
                       return "Try again";
               }
       }
   };
}

main() {
       var game = numberGame();
       print( game.guess(45) );
}
{{{code}}}

This is not possible with Dart, because in this case JavaScript would return an Object with a new function.

As an alternative approach, Dart might be benefit from implementing anonymous classes. Like:

{{{code}}}
 
interface A {
    void doSomething();
}

myFunction() {
   return new A() {
         void doSomething() {
            // do something
         }
   }
}

numberGame() {
   return new Dynamic() {
      int guess(g) {
      }
   }
}

{{{/code}}}

This is a known appoach even in the Java World.

Please see:
https://groups.google.com/a/dartlang.org/group/misc/browse_thread/thread/891044daf1754150

[iposva-google]

Set owner to @gbracha.
Added Area-Language, Triaged labels.

[gbracha]

We may consider object literals in due course. Renaming the issue since it has nothing to do with the title.

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Removed Type-Defect label.
Added Type-Enhancement, Accepted labels.
Changed the title to: "Support object literals or anonymous classes".

[gbracha]

Issue #3028 has been merged into this issue.

[gbracha]

You can emulate this easily enough with a class being constructed with a closure argument to capture scope etc. Benefit outweighed by complexity.

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Added WontFix label.

[DartBot]

This comment was originally written by @tomyeh

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Sorry, I don't get it. Would you show me the sample code equivalent to anonymous classes? For example, how to do the following code in Dart? Thanks.

return new Iterator<String>() {
  bool hasNext() {...}
  String next() {...}
};

[DartBot]

This comment was originally written by [email protected]

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Tom,

I already started a thread about this issue. https://groups.google.com/a/dartlang.org/forum/#!topic/misc/rUWJMuDfJWc

[bugeats]

Bummer this didn't happen.

[AdamSalma]

I guess we're trying to go the Java route here 😓 Put the complexity on the end user instead of designing software correctly - bravo