Filtering array of custom objects

From what I can see from your question, none of the above really has any connection to Objective-C. Your example contains a few other issues, however, keeping it from working as intended.

• MyObject has no initializer (as of Swift 2.2, you should include at least one initializer).
• What are obj1, obj2, ... ? You treat these as methods or class/structures types, when I presume you're intending for these to be instances of the MyObject type.

If fixing the above, the actual filtering part of your code will work as intended (note that you can omit () from filter() {... }), e.g.:

enum ObjectType{
    case type1
    case type2
    case type3
}

class MyObject {
    var type : ObjectType
    let id: Int
    init(type: ObjectType, id: Int) {
        self.type = type
        self.id = id
    }
}

let array = [MyObject(type: .type1, id: 1),
             MyObject(type: .type2, id: 2),
             MyObject(type: .type3, id: 3),
             MyObject(type: .type2, id: 4),
             MyObject(type: .type3, id: 5)]

let type2Array = array.filter { $0.type == .type2}
type2Array.forEach { print($0.id) } // 2, 4

As an alternative to filtering directly to an enumeration case, you could specify the rawValue type of your enumeration and match to this instead. E.g. using an Int rawValue allows you to (in addition to filtering w.r.t. rawValue) perform pattern matching for say, ranges of cases in your enumeration.

enum ObjectType : Int {
    case type1 = 1  // rawValue = 1
    case type2      // rawValue = 2, implicitly
    case type3      // ...
}

class MyObject {
    var type : ObjectType
    let id: Int
    init(type: ObjectType, id: Int) {
        self.type = type
        self.id = id
    }
}

let array = [MyObject(type: .type1, id: 1),
             MyObject(type: .type2, id: 2),
             MyObject(type: .type3, id: 3),
             MyObject(type: .type2, id: 4),
             MyObject(type: .type3, id: 5)]

/* filter w.r.t. to rawValue */
let type2Array = array.filter { $0.type.rawValue == 2}
type2Array.forEach { print($0.id) } // 2, 4

/* filter using pattern matching, for rawValues in range [1,2],
   <=> filter true for cases .type1 and .type2 */
let type1or2Array = array.filter { 1...2 ~= $0.type.rawValue }
type1or2Array.forEach { print($0.id) } // 1, 2, 4