swift Equatable 的缺省实现

Starting from Swift 4.1, all you have to is to conform to the Equatable protocol without the need of implementing the == method. See: SE-0185 - Synthesizing Equatable and Hashable conformance.

Example:

Keep in mind that the default behavior for the == is to compare all the type properties (based on the example: lhs.id == rhs.id && lhs.value == rhs.value). If you are aiming to achieve a custom behavior (comparing only one property for instance), you have to do it by yourself:

At this point, the equality would be based on the id value, regardless of what's the value of value.

https://stackoverflow.com/questions/37541512/swift-struct-doesnt-conform-to-protocol-equatable

猜测：下面两者的签名形式应该是相同的

/// Represents a response to a `MoyaProvider.request`.

public final class Response: CustomDebugStringConvertible, Equatable {

public static func == (lhs: Response, rhs: Response) -> Bool {

return lhs.statusCode == rhs.statusCode

&& lhs.data == rhs.data

&& lhs.response == rhs.response

}

}

public func ==(lhs: ConstraintItem, rhs: ConstraintItem) -> Bool {

// pointer equality

guard lhs !== rhs else {

return true

}

// must both have valid targets and identical attributes

guard let target1 = lhs.target,

let target2 = rhs.target,

target1 === target2 && lhs.attributes == rhs.attributes else {

return false

}

return true

}