Overloading equivalence (==) operator for custom class in Swift

问题

Is it possible to overload equivalence (==) operator for a custom class inside that custom class. However I know that it is possible to have this operator overloaded outside class scope. Appreciate any sample code. Thanks in advance.

回答1:

Add global functions. For example:

class CustomClass {
    var id = "my id"
}

func ==(lhs: CustomClass, rhs: CustomClass) -> Bool {
    return lhs == rhs
}
func !=(lhs: CustomClass, rhs: CustomClass) -> Bool {
    return !(lhs == rhs)
}

To conform Equatable protocol in Swift 2

class CustomClass: Equatable {
    var id = "my id"
}

func ==(left: CustomClass, right: CustomClass) -> Bool {
    return left.id == right.id
}

To conform Equatable protocol in Swift 3

class CustomClass {
    var id = "my id"
}

extension CustomClass: Equatable {
    static func ==(lhs: CustomClass, rhs: CustomClass) -> Bool {
        return lhs.id == rhs.id
    }
}

回答2:

No, operators are overloaded using global functions.

来源：https://stackoverflow.com/questions/28848119/overloading-equivalence-operator-for-custom-class-in-swift