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How do we print variable name in swift? It's similar to what this question discusses Get a Swift Variable's Actual Name as String I can't figure out from above QA how to print it in swift for my need as described below

struct API {
    static let apiEndPoint = "example.com/profile?"
    static let apiEndPoint1 = "example.com/user?"
 }

doSomething(endPoint: API.apiEndPoint)
doSomething(endPoint: API.apiEndPoint1)

func doSomething(endPoint: String) {
    // print the variable name which should be apiEndPoint or endPoint1
}
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8
  • 1
    print("apiEndPoint")? Commented Jan 30, 2020 at 19:16
  • 1
    You should use a dictionary instead of a variable, if you don't want to hardcode variable names in print calls. Commented Jan 30, 2020 at 19:17
  • 6
    There's no way to do what you've literally asked for, but there are several approaches to doing similar things. What are you trying to acheve? Commented Jan 30, 2020 at 19:17
  • I've updated my question. I said I just want to print the variable name. Commented Jan 30, 2020 at 19:21
  • 1
    No. From the point of view of your doSomething method, all it sees is the value of its endPoint parameter. Where that came from, a variable, a constant, a function call, whatever, is not visible to it. Commented Jan 30, 2020 at 19:36

3 Answers 3

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5

You could change your struct to an enum

enum API: String {
    case apiEndPoint = "example.com/profile?"
    case apiEndPoint1 = "example.com/user?"
 }


func doSomething(endPoint: API) {
    print("\(endPoint): \(endPoint.rawValue)")
}

Example

doSomething(endPoint: .apiEndPoint)

apiEndPoint: example.com/profile?

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3 Comments

You are spot on but for me changing struct to enum will require a lot of code changes.
@Raymond Maybe so but an enum could give you code that is easier to read and more type safe but of course I have no idea how much work it would be
@Raymond More code changes than any other method? This is exactly the sort of thing enums are meant for, anything else is just making it needlessly complicated.
2

You could use Mirror for reflection and do something silly like this:

struct API {
    let apiEndPoint = "example.com/profile?"
    let apiEndPoint1 = "example.com/user?"
}

func doSomething(api: API, endPoint: String) {
    let mirror = Mirror(reflecting: api)

    for child in mirror.children {
        if (child.value as? String) == endPoint {
            print(child.label!) // will print apiEndPoint
        }
    }
}

let api = API()

doSomething(api: api, endPoint: api.apiEndPoint)
doSomething(api: api, endPoint: api.apiEndPoint1)

But I would never recommend doing something like this, and using an enum like the other answer suggested is probably the way to go.

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7 Comments

Yes I've seen this solution but it's not practical as I've hundreds of endpoints and I'll end up writing hundreds of if else conditions.
@Raymond don't know why this would make you need 100s of if/else's - it will work for any number of endpoints with no need for extra ifs
Sorry I missed it. Yes you are right. However it's not working for me. Please note that I'm not passing api to function, I'm only passing endPoint. I tired by doing let mirror = Mirror(reflecting: API()) but it didn't work, control doesn't go inside the if condition.
@Raymond yeah, I had to add api as a parameter if you wanted it to work right, which is another reason I would suggest an enum instead since it is much cleaner. That said if the endpoints are constant let values that never change, I don't see why let mirror = Mirror(reflecting: API()) would not work, it works for me in my playground.
@Raymond Is mirror.children empty? Any chance your API let's are static?
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1

I like Quinn's approach, but I believe it can be done more simply:

struct API {
    let apiEndPoint = "example.com/profile?"
    let apiEndPoint1 = "example.com/user?"

    func name(for string: String) -> String? {
        Mirror(reflecting: self).children
            .first { $0.value as? String == string }?.label
    }
}

func doSomething(endPoint: String) {
    print(API().name(for: endPoint)!)
}

let api = API()

doSomething(endPoint: api.apiEndPoint) // apiEndPoint
doSomething(endPoint: api.apiEndPoint1) // apiEndPoint1
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3 Comments

It crashes on print(API().name(for: endPoint)!). Thread 12: Fatal error: Unexpectedly found nil while unwrapping an Optional value. Please note that I've static variables in structure. Also I don't use api = API() to pass api value in the function. I directly pass API.endPoint as I've written in question.
@Raymond it is because your variables are static, static variables don't appear in reflection so it is finding nothing and returning null
Agreed; this is likely not solvable for static properties or globals without adding some piece of metadata somewhere (creating a lookup Dictionary or creating a struct with the name and the path, for example).

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