Equatable

可以进行值相等比较的类型。

protocol Equatable

比较两个类是否相等

class StreetAddress {
    let number: String
    let street: String
    let unit: String?


    init(_ number: String, _ street: String, unit: String? = nil) {
        self.number = number
        self.street = street
        self.unit = unit
    }
}

extension StreetAddress: Equatable {
    static func == (lhs: StreetAddress, rhs: StreetAddress) -> Bool {
        return
            lhs.number == rhs.number &&
            lhs.street == rhs.street &&
            lhs.unit == rhs.unit
    }
}

对于结构，其所有存储的属性都必须符合Equatable。
对于枚举，其所有关联值都必须符合Equatable。
基本数据类型是都符合Equatable的,因此多个类时需要都实现Equatable。

class StreeAddress{
    let number : String
    let street : String
    let unit : String?
    let demo : Demo
    
    init(_ number : String , _ street : String , _ name : String, _ unit : String? = nil) {
        self.number = number
        self.street = street
        self.unit = unit
        self.demo = Demo(name)
    }
}


class Demo{
    let name : String
    
    init(_ name : String = "名字") {
        self.name = name
    }
}

extension StreeAddress : Equatable{
    static func == (lhs: StreeAddress, rhs: StreeAddress) -> Bool {
        return
            lhs.number == rhs.number &&
            lhs.street == rhs.street &&
            lhs.unit == rhs.unit &&
            lhs.demo == rhs.demo
    }
}

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