Swift Array.insert generics

Question

func getIndex(valueToFind: T) -> Int? {...}

mutating func replaceObjectWithObject(obj1: T, obj2: T) {
    if let index =          


        

Answer 1

This is actually not possible via an extension under the existing system of protocols and generics in Swift - you can't add additional constraints to the generic subtype of a type, so you can't extend Array with a method that requires that its contents conform to Equatable.

You can see this restriction in action with the built-in Array type -- there's no myArray.find(element) method, but there is a global function find() that takes a collection and an element, with a generic constraint that the collection's elements are Equatable:

func find(domain: C, value: C.Generator.Element) -> C.Index?

You can do this for your method - you just need to write a similar top-level function:

func replaceObjectWithObject(inout collection: C, obj1: C.Generator.Element, obj2: C.Generator.Element) {
    if let index = find(collection, obj1) {
        removeAtIndex(&collection, index)
        insert(&collection, obj2, atIndex: index)
    }
}

var myArray = [1, 2, 3, 4, 5]
replaceObjectWithObject(&myArray, 2, 7)
// 1, 2, 7, 4, 5