NOT condition in 'if case' statement

Question

I have an enum:

enum E {
    case A, B, C(Int)
}

let a: E = .A

Here\'s how I would check if a equals .B

Answer 1

You are using single = sign which is an assignment operator. You have to use double == which is a comparison one and don't use case .A, use E.A is the right way to do that:

if E.A == a {
    // works fine
    print("1111")
}

if E.B != a {
    // works fine
    print("2222")
}

if E.B == a {
    // works fine
    print("3333")
}

Extended:

To make it works with associated values you have to implement Equatable protocol, example:

extension E: Equatable {}
func ==(lhs: E, rhs: E) -> Bool {
    switch (lhs, rhs) {
        case (let .C(x1), let .C(x2)):
            return x1 == x2
        case (.A, .A):
        return true

     default:
         return false
    }
}

Of course you have to handle all of the possibilities but I think you have an idea.

Extended:

I don't get your comment but this works for me fine:

enum E {
    case A, B, C(Int)
}

extension E: Equatable {}
func ==(lhs: E, rhs: E) -> Bool {
    switch (lhs, rhs) {
        case (let .C(x1), let .C(x2)):
            return x1 == x2
        case (.A, .A):
            return true
        case (.B, .B):
            return true

     default:
         return false
    }
}

let a: E = .A
let b: E = .B
let c: E = .C(11)

if E.A == a {
    // works fine
    print("aaa true")
}
if E.A != a {
    // works fine
    print("aaa false")
}

if E.B == b {
    // works fine
    print("bbb true")
}

if E.B == b {
    // works fine
    print("bbb false")
}

if E.C(11) == c {
    // works fine
    print("ccc true")
}

if E.C(11) != c {
    // works fine
    print("1 ccc false")
}

if E.C(22) != c {
    // works fine
    print("2 ccc false")
}