How can I use contains function in Array extension in Swift? [duplicate]

Question

I am using contains function in a function which array is a string array, like this:

func addArrayCheck(array: Array<String>, value: String) {
    if (array.contains(value)) {
        print("Element exists!")
    }
    else {
        print("Element does not exists!")
    }
}

Then I tried to make an extension, but Xcode complain about this:

Missing argument label 'where:' in call

extension Array {
    func addArrayCheck(value: Self.Element) {
        if self.contains(value) {
            print("Element exists!")
        }
        else {
            print("Element does not exists!")
        }
    }
}

Why I cannot use contains like I used in function in generic form? and how can I solve the issue?

Answer 1

That contains overload only works when your elements are Equatable.

extension Sequence where Element: Equatable {
  func addCheck(value: Element) {
    print(
      contains(value)
        ? "Element exists!"
        : "Element does not exist!"
    )
  }
}