reverberating-performance-7459

readme.md

reverberating-performance-7459

Created with <3 with dartpad.dev.

main.dart

void main() {
  print('DartWhen');

  var x = 1;

  when(x, {
    1: () => print("is 1"),
    2: () => print("is 2"),
    3: () {
      print("is 3");
      print("Code block");
    },
    x > 500: () => print("> 500"),
    Default: () => print("default - no match")
  });

  var y = when(x, {1: 11, 2: 22, 3: 33, x > 500: 0, Default: -1});

  print("y: $y");
}

class Default {}

dynamic when<T>(T condition, Map<dynamic, dynamic> branches) {
  var consumed = false;
  dynamic returnValue;
  branches.forEach((key, value) {
    if (key.runtimeType == condition.runtimeType && key == condition) {
      if (value is Function) {
        value.call();
        consumed = true;
      } else {
        returnValue = value;
        consumed = true;
      }
    } else if (key.runtimeType == bool && key as bool == true) {
      if (value is Function) {
        value.call();
        consumed = true;
      } else {
        returnValue = value;
        consumed = true;
      }
    }
  });

  if (consumed) {
    return returnValue;
  } else {
    if (branches.containsKey(Default)) {
      branches[Default].call();
    }
  }
}