How can I get the index of an object in an array with a property value that matches a specific criteria?

Question

Maybe this question has already been answered before or the answer is so obvious but I've been searching for days and cannot find an answer to this problem. I would appreciate any help on this as I'm at my wits' end.

class marker {
    var latitude = Double()
    var longitude = Double()
    var coordinate = CLLocationCoordinate2DMake(latitude, longitude)
}

let someCoordinate = CLLocationCoordinate2DMake(someLatitude, someLongitude)

Now let's say that I have an array named "markers" of 10 marker objects with all properties already initialized. How can I find the index of the marker item whose coordinate value matches the value of someCoordinate?

EDIT

While trying out the suggestion of iosdk below, I found out that I was trying to compare the marker.coordinate property which is a CLLocationCoordinate2D. That did not work as I expected. Instead I tried this and it worked:

let markerIndex = indexOfMarker(markers) { $0.position.latitude == latitude && $0.position.longitude == longitude }

Answer 1

struct SomeStruct {
  let a, b: Int
}

let one = SomeStruct(a: 1, b: 1)
let two = SomeStruct(a: 2, b: 2)
let three = SomeStruct(a: 3, b: 3)

let ar = [one, two, three]

let ans = ar.indexOf { $0.a == 2 } // 1?

Or, on Swift 1, the indexOf function can be:

func indexOfOld<S : SequenceType>(seq: S, predicate: S.Generator.Element -> Bool) -> Int? {

  for (index, value) in enumerate(seq) {
    if predicate(value) {
      return index
    }
  }
  return nil
}

And you'd replace the last line above with:

let ans = indexOfOld(ar) { $0.a == 2 } // 1?