如何解决“二元运算符”=='不能应用于两个'Foo'操作数“？ [英] How to resolve "Binary operator '==' cannot be applied to two 'Foo' operands"?

问题描述

我按如下方式创建了一个类Foo：

I created a class Foo as follows:

class Foo{

    var randomeVar:String?

    func saySomething(){
        print("Something")
    }
}

我现在想要比较foo的不同实例，如下所示：

I now want to compare different instances of foo as follows:

let foo1 = Foo()
let foo2 = Foo()
if foo1 == foo2{
    print("Cool")
}

当我这样做时，遵守二元运算符'=='不能应用于两个'Foo'操作数的投诉。问题是什么以及如何解决？

When I do so however the complies complaints that "Binary operator '==' cannot be applied to two 'Foo' operands". What is the problem and how do I fix it?

推荐答案

Foo没有任何具有任何属性的父类来执行比较，所以它不知道如何比较自己。

Foo has no parent class that has any properties to perform comparison, so it has no idea how to compare itself.

相反，您需要采用Equatable协议，然后告诉您包含 == 运算符，此时您将定义您的操作：

Instead you need to adopt the Equatable protocol, which will then tell you to include the == operator, at which point you would define your action:

您的其他选项是使用===，它将比较引用，因此唯一的方法就是这两个项目都指向同一个实例。

Your other option is to use ===, which will compare the references, so the only way this will pass is both items are pointing to the same instance.

class Foo : Equatable{

    var randomeVar:String?

    func saySomething(){
        print("Something")
    }

    static func ==(lhs: Foo, rhs: Foo) -> Bool
    {
      //what makes us equal
    }
}

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