成员操作符'=='必须至少有一个参数类型

Question

我试图在equalityClass中实现Equatable协议，但显示成员操作符'=='必须至少有一个类型为'eqaualityClass'的参数 .can任何人解释什么是错误的？

protocol Rectangle: Equatable { 

    var width: Double { get } 
    var height: Double { get } 

} 

class eqaualityClass:Rectangle{ 

    internal var width: Double = 0.0 
    internal var height: Double = 0.0 

     static func == <T:Rectangle>(lhs: T, rhs: T) -> Bool { 
      return lhs.width == rhs.width && rhs.height == lhs.height 
    } 
} 

Answer 1

您需要使您的Rectangle协议成为一个类。试试这样：

protocol Rectangle: class, Equatable { 
    var width: Double { get } 
    var height: Double { get } 
} 

class Equality: Rectangle { 
    internal var width: Double = 0 
    internal var height: Double = 0 
    static func ==(lhs: Equality, rhs: Equality) -> Bool { 
     return lhs.width == rhs.width && rhs.height == lhs.height 
    } 
} 

或

protocol Rectangle: class, Equatable { 
    var width: Double { get } 
    var height: Double { get } 
} 

extension Rectangle { 
    static func ==(lhs: Self, rhs: Self) -> Bool { 
     return lhs.width == rhs.width && rhs.height == lhs.height 
    } 
} 

class Equality: Rectangle { 
    internal var width: Double = 0 
    internal var height: Double = 0 
}