How are arguments moved in bulk from one function to another, in Dart?

Question

In Javascript, one can use apply to move arguments in bulk from one function to another? How is this done in Dart?

To use a mismatch of Dart and Javascript:

Object proxy(<any number and type of arguments>) {
    if(feelGood) 
        return goodFunc.apply(arguments);
    else 
        return badFunc.apply(arguments);
}

In Dart, how does one

• specify any number and type of arguments?

• apply the arguments from one function to another?

Answer 1

You can't create a function that takes any number of arguments in Dart. For that, you have to fall back on noSuchMethod. To call a function with a dynamic list of arguments, you can use Function.apply.

Example:

class _MyProxy implements Function {
  const _MyProxy();
  noSuchMethod(InvocationMirror m) {
    if (m.memberName != #call) return super.noSuchMethod(m);
    return Function.apply(feelGood ? goodFunc : badFunc, m.positionalArguments, m.namedArguments);
  }
}
const Function proxy = const _MyProxy();

This class captures invalid calls using noSuchMethod. It acts as a function by intercepting the "call" method. It then works as your proxy method intends by forwarding the arguments to either goodFunc or badFunc using Function.apply.

You can then write:

proxy(<any number and type of argument>);

and have it call either goodFunc or badFunc with those exact arguments.

Answer 2

You can use Function.apply :

main() {
  final l = [];
  Function.apply(l.add, ['v1']);
  print(l);  // display "[v1]"
}

Dart does not support varargs on method but you can simulate them with noSuchMethod (see Creating function with variable number of arguments or parameters in Dart)