What exactly is type `(val: string)` in Swift when calling `type(of: xxx)`

I am running the follow function on a particular custom type:

    let mirror = Mirror(reflecting: self)
    print("self \(self)");

    for (propName, propValue) in mirror.children {
        print("propname \(propName) ... \(propValue)", type(of: propValue))
    }

And it is printing out

self UserAuthInput.userEmail(val: [email protected])
propname Optional("userEmail") ... (val: "[email protected]") (val: String)

I am having a hard time wrapping my head around as a Swift newb what exactly (val: string) type means. I know it came from a definition like this:

    public enum UserAuthInput {

        case userEmail(val: String)

        case userPhone(val: String)
    }

However my question is,

1) How can I parse the [email protected] out of the (val: string) type object propValue?

2) How can I check that this particular self is of enum type thus special handling is needed?

Thank you!

Solution

It's a one-element tuple. This is confirmed by using another mirror to reflect the child's value:

let mirror = Mirror(reflecting: UserAuthInput.userEmail(val: "[email protected]"))
for (propName, propValue) in mirror.children {
    print("propname \(propName!) ... \(propValue)", type(of: propValue))
    let subMirror = Mirror(reflecting: propValue)
    print(subMirror.displayStyle!) // tuple

    // this is one way you can get its value
    print(subMirror.children.first!.value) // [email protected]
}

Normally you can't create one-element tuples, so I'm quite surprised by this too. Since you can't use the type (val: String) in code, you can't get the associated value's value by simply casting. One way, which I've shown above, is to use another mirror.

This is consistent with the case of 2 or more associated values, which also makes propValue be of a tuple type.

public enum UserAuthInput {

    case userEmail(val: String, val2: String)

    case userPhone(val: String)
}

let mirror = Mirror(reflecting: UserAuthInput.userEmail(val: "[email protected]", val2: "hello"))
for (_, propValue) in mirror.children {
    print(type(of: propValue) == (val: String, val2: String).self) // true
}

To check whether the mirror is reflecting an enum, check displayStyle:

if mirror.displayStyle == .enum {
    // enum!
}