class01 func

class01func.dart

void main(){
  
  /// 1
  void func0(){ 
    // ...
  }
  void func1(){
    // ...
    return;
  }
  void func2() => 0;
  int func3() => 1;
  
  
  func0();
  func1();
  func2();
  func3();
  
  
  /// 2
  void Function() func4 = (){};
  void Function() func5 = () => 5;
  int Function() func6 = (){
    return 6;
  };
  int Function() func7 = () => 7;
  
  func4();
  func5();
  func6();
  func7();
  
  
  /// 3 P&A
  void fpa0(int arg){}
  void fpa1(int arg0, arg1, var arg2) => print("$arg0 $arg1 $arg2");
  
  // fpa0(); // err -> arg
  // fpa1();  // err -> arg0,1,2
  fpa0(0);
  fpa1(1,2,3);
  
  
  /// 4 Named P&A
  void fnpa0({int? arg}){}
  void fnpa1({required int? arg}){}
  void fnpa2({required int arg}){}
  
  fnpa0();
  // fnpa0(0); // err -> named
  fnpa0(arg: 0);
  
  // fnpa1(); // err -> required
  fnpa1(arg: null);
  fnpa1(arg: 1);
  
  // fnpa2(); // err -> arg
  // fnpa2(arg: null); // err -> not null
  fnpa2(arg: 2);
  
  
  /// 5 callback
  void fcb(void Function() cb) => cb();
  fcb(() => print("cb0"));
  
  void fcb1(void Function(int, String) cb) => cb(1, "fcb1 - cb");
  fcb1((int x, String y) => print("$x $y"));
  
  int fcb2(int Function(int) cb) => cb(2) + 1;
  int fcb2Value = fcb2((int z) => z+z);
  print("fcb2Value + 1 = ${fcb2Value+1}");
  
}