class SomeClass {

	Dictionary<String, GMSMarker> dict; // I dunno the syntax check it yourself.

	func createMarker(id: String, position: ??) {
		let marker = GMSMarker(position: position)
		dict.put(id, marker)
	}

	func modifyMarker(id: String) {
		let marker = dict.get(id)
        // do stuff to marker
	}

	func deleteMarker(id: String) {
		let marker = dict.get(id)
		marker.map = nil
	}
}