dart 是否支持运算符重载 [英] Does dart support operator overloading

问题描述

我读到 Dart 不支持函数重载.它是否支持运算符重载?如果是，你能在一个简单的例子中告诉我它是如何完成的吗?以及有哪些优势等?

I read that Dart does not support function overloading. Does it support operator overloading? If yes, can you show me how it's done in a simple example? And what are some advantages etc?

推荐答案

在新版本中使用 == 运算符尝试重载时，所选答案不再有效.现在你需要这样做:

The chosen answer is no longer valid when you try overloads using the == operator in the new version. Now you need to do this:

class MyClass {
  @override
  bool operator ==(other) {
    // compare this to other
  }
}

但这并不安全.other 未指定为类型，可能会发生意外.例如:

But it's not safe. other is not specified as a type, Something unexpected may happened. For example:

void main() {
  var a = A(1);
  var b = B(1);
  var result = a == b;
  print(result); //result is true
}

class A {
  A(this.index);

  final int index;

  @override
  bool operator ==(other) => other.index == index;
}

class B {
  B(this.index);

  final int index;
}

所以你可以这样做:

class A {
  A(this.index);

  final int index;

  @override
  bool operator ==(covariant A other) => other.index == index;
}

你需要使用covariant.因为 Object 重载了 == 运算符.

You need to use covariant. Because Object overloads the == operator.

测试对象类型:
访问:hash_and_equals

class A {
  A(this.index);

  final int index;

  @override
  bool operator ==(other) => other is A && (other.index == index);

  @override
  int get hashCode => index;
}

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