Swift Struct doesn't conform to protocol Equatable?

Question

How do I make a structure conform to protocol \"Equatable\"?

I\'m using Xcode 7.3.1

struct MyStruct {
   var id: Int
   var value: String

   init(id: In         


        

Answer 1

The issue isn't that the struct is within a class. That is certainly allowable, and there are many instances where you might want to do that. The issue is in the implementation of the Equatable protocol. You have to give a global implementation of == (which you have done), but there is no entity MyStruct....it is ParentClass.MyStruct (if the struct is defined within a parent class). The example below in itself is probably not a good example in this case, but it does show how you can do this if needed.

class ParentClass {

  struct MyStruct {
    var id: Int
    var value: String

    init(id: Int, value: String) {
      self.id = id
      self.value = value
    }

    var description: String {
      return "blablabla"
    }
  }
}

extension ParentClass.MyStruct: Equatable {}

func ==(lhs: ParentClass.MyStruct, rhs: ParentClass.MyStruct) -> Bool {
  let areEqual = lhs.id == rhs.id &&
    lhs.value == rhs.value

  return areEqual
}

let s1 = ParentClass.MyStruct(id: 1, value: "one")
let s2 = ParentClass.MyStruct(id: 2, value: "two")
let s3 = ParentClass.MyStruct(id: 1, value: "one")

s1.description    //blablabla

s1 == s2         //false
s3 == s1         //true

Note: I like to implement Comparable rather than just Equatable, which will allow you to support sorting and other functionality.