Sample 1: both `==` and `!=` is true.
import Foundation
class Foo:NSObject {
let name:String
init(name:String) {
self.name = name
}
public static func ==(lhs: Foo, rhs: Foo) -> Bool {
guard type(of:lhs) == type(of:rhs) else { return false }
return lhs.name == rhs.name
}
}
let a = Foo(name: "bar")
let b = Foo(name: "bar")
print(a == b) // true
print(a != b) // true
Sample 2: Add above code to a do-block, behavior changes to expect
do {
class Foo:NSObject {
let name:String
init(name:String) {
self.name = name
}
public static func ==(lhs: Foo, rhs: Foo) -> Bool {
guard type(of:lhs) == type(of:rhs) else { return false }
return lhs.name == rhs.name
}
}
let a = Foo(name: "bar")
let b = Foo(name: "bar")
print(a == b) // false
print(a != b) // true
}
Sample 3: A little investigation shows that `==` didn't call NSObject's `
func isEqual(_ object: Any?) -> Bool` but `!=` did.
class Foo:NSObject {
let name:String
init(name:String) {
self.name = name
}
public static func ==(lhs: Foo, rhs: Foo) -> Bool {
guard type(of:lhs) == type(of:rhs) else { return false }
return lhs.name == rhs.name
}
override func isEqual(to object: Any?) -> Bool {
print("111")
return super.isEqual(to: object)
}
override func isEqual(_ object: Any?) -> Bool {
print("2222")
return super.isEqual(object)
}
}
let a = Foo(name: "bar")
let b = Foo(name: "bar")
print(a == b) // true
print(a != b) // 2222, true
print(!(a == b)) // false
So I am wondering what is the future? Will we keep on using `isEqual(_
object: Any?)` with class that inherits `NSObject`, or we are trying to
drop it?
Xcode 8.3.1 (8E1000a), 3.1 (swiftlang-802.0.51 clang-802.0.41), macOS 10.12.4
(16E195)
Zhaoxin
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