Swift 4.1 (and above) Updated answer:

Starting from Swift 4.1, all you have to is to conform to the Equatable protocol without the need of implementing the == method. See: SE-0185 - Synthesizing Equatable and Hashable conformance.

Example:

struct MyStruct: Equatable {    var id: Int    var value: String}let obj1 = MyStruct(id: 101, value: "object")let obj2 = MyStruct(id: 101, value: "object")obj1 == obj2 // true

Keep in mind that the default behavior for the == is to compare all the type properties (based on the example: lhs.id == rhs.id && lhs.value == rhs.value). If you are aiming to achieve a custom behavior (comparing only one property for instance), you have to do it by yourself:

struct MyStruct: Equatable {    var id: Int    var value: String}extension MyStruct {    static func ==(lhs: MyStruct, rhs: MyStruct) -> Bool {        return lhs.id == rhs.id    }}let obj1 = MyStruct(id: 101, value: "obj1")let obj2 = MyStruct(id: 101, value: "obj2")obj1 == obj2 // true

At this point, the equality would be based on the id value, regardless of what's the value of value.

OK, after lots of searching, it's working...

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

My Struct was in a class, so it didn't work.. I moved this Struct out of my class and now it's good :)

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    //blablablas1 == s2         //falses3 == s1         //true

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