如何比较同一Swift枚举的不同实例？

Question

Take this enum and the three literal instances of it that follow:

enum Types {
    case string(String), int(Int), bool(Bool)
}

let t1 = Types.string("one")
let t2 = Types.string("two")
let t3 = Types.int(3)

How can these be compared so that t1 and t2 match (as the same enum case, even though their values differ), whilst t1 and t3 do not match (as they are different cases of the same enum), like this?:

func compare (lhs: Types, rhs: Types) -> Bool {
    return lhs == rhs
}

print(compare(lhs: t1, rhs: t2)) // prints "true"
print(compare(lhs: t1, rhs: t3)) // prints "false"

Answer 1

You can achieve that by conforming Types to Equatable protocol:

extension Types: Equatable {
    static func == (lhs: Types, rhs: Types) -> Bool {
        switch (lhs, rhs) {
        case (.string, .string), (.int, .int), (.bool, .bool):
            return true
        default:
            return false
        }
    }
}

print(t1 == t2) // true
print(t1 == t3) // false

---

UPD.

You should think about formatting your code. Swift api design guidelines said:

Follow case conventions. Names of types and protocols are UpperCamelCase. Everything else is lowerCamelCase.

So, there is no uppercase case s should appear in your code.

Spaces between parentheses should be trimmed as well.

---

UPD 1.

if I want to get the value "one" out of let t1 = Types.String( "one" ), is that possible and if so how?

Sure. The if case let ... can help you here:

if case let .string(value) = t1 {
    print(value) // "one"
}