代码之家 › 专栏 › 技术社区 › Shubhamhackz

dart中没有这样的方法?

dart-pub dart

1

Shubhamhackz · 技术社区 · 7 年前

尝试使用noSuchMethod()时收到警告。

 void main() {
    var person = new Person();
    print(person.missing("20", "Shubham")); // is a missing method!
 }

 class Person {

    @override
    noSuchMethod(Invocation msg) => "got ${msg.memberName} "
                      "with arguments ${msg.positionalArguments}";

 }

2 回复 | 直到 7 年前

1

5

Shubhamhackz 7 年前

根据调用未实现方法的官方文档,您必须满足以下几点之一:

接收机为静态型动态型。
接收器具有定义未实现方法的静态类型 (抽象是可以的),并且接收器的动态类型具有 noSuchMethod()的实现与类中的实现不同对象

例1:首先满足点

class Person {
  @override  //overring noSuchMethod
    noSuchMethod(Invocation invocation) => 'Got the ${invocation.memberName} with arguments ${invocation.positionalArguments}';
}

main(List<String> args) {
  dynamic person = new Person(); // person is declared dynamic hence staifies the first point
  print(person.missing('20','shubham'));  //We are calling an unimplemented method called 'missing'
}

例2:满足第二点

class Person {
  missing(int age,String name);

  @override //overriding noSuchMethod
    noSuchMethod(Invocation invocation) => 'Got the ${invocation.memberName} with arguments ${invocation.positionalArguments}';
}

main(List<String> args) {
  dynamic person = new Person(); //person could be var, Person or dynamic
  print(person.missing(20,'shubham')); //calling abstract method
}