Question

Is there a way to test the existence of a function or method in Dart without trying to call it and catch a NoSuchMethodError error?
I am looking for something like

if (exists("func_name")){...}

to test whether a function namedfunc_nameexists.
Thanks in advance!

Answer 1

You can do that with mirrors API :

import 'dart:mirrors';

class Test {
  method1() => "hello";
}

main() {
  print(existsFunction("main")); // true
  print(existsFunction("main1")); // false
  print(existsMethodOnObject(new Test(), "method1")); // true
  print(existsMethodOnObject(new Test(), "method2")); // false
}

bool existsFunction(String functionName) => currentMirrorSystem().isolate
    .rootLibrary.functions.containsKey(functionName);

bool existsMethodOnObject(Object o, String method) => reflect(o).type.methods
    .containsKey(method);

existsFunction only tests if a function with functionName exists in the current library. Thus with functions available by import statement existsFunction will return false.