Creating function with variable number of arguments or parameters in Dart

Question

I am looking for a way to create a function with a variable number of arguments or parameters in Dart. I know I could create an array parameter instead, but I would prefer to not do that because I'm working on a library where syntactic brevity is important.

For example, in plain JavaScript, we could do something like this (borrowed from here):

function superHeroes() {   for (var i = 0; i < arguments.length; i++) {     console.log("There's no stopping " + arguments[i]);   } }  superHeroes('UberMan', 'Exceptional Woman', 'The Hunk'); 

However, in dart, that code will not run. Is there a way to do the same thing in dart? If not, is this something that is on the roadmap?

Answer 1

You can't do that for now.

I don't really know if varargs will come back - they were there some times ago but have been removed.

However it is possible to emulate varargs with Emulating functions. See the below code snippet.

typedef OnCall = dynamic Function(List arguments);  class VarargsFunction {   VarargsFunction(this._onCall);      final OnCall _onCall;    noSuchMethod(Invocation invocation) {     if (!invocation.isMethod || invocation.namedArguments.isNotEmpty)       super.noSuchMethod(invocation);     final arguments = invocation.positionalArguments;     return _onCall(arguments);   } }  main() {   final superHeroes = VarargsFunction((arguments) {     for (final superHero in arguments) {       print("There's no stopping ${superHero}");     }   }) as dynamic;   superHeroes('UberMan', 'Exceptional Woman', 'The Hunk'); } 

Answer 2

Dart does indirectly support var-args as long as you as you aren't too much into syntactic brevity.

void testFunction([List<dynamic> args=[]]) {   for(dynamic arg:args)   {     // Handle each arg...   } }  testFunction([0, 1, 2, 3, 4, 5, 6]); testFunction(); testFunction([0, 1, 2]); 

Note: You can do the same thing with named parameters, but you'll have to handle things internally, just in case if the user (of that function; which could be you) decides to not pass any value to that named parameter.

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I would like to thank @Ladicek for indirectly letting me know that a word like brevity exists in English.