Here is a Gist I posted showing a Swift utility function that enables you to create a Dictionary containing an optional entry for every element in an Array. It uses the reduce function to create one Dictionary from every element in an Array, based on a closure you provide that turns an array element into a key-value tuple.
This code was compiled and tested against Xcode 6 Beta 3.
| /** | |
| Creates a dictionary with an optional | |
| entry for every element in an array. | |
| */ | |
| func toDictionary<E, K, V>( | |
| array: [E], | |
| transformer: (element: E) -> (key: K, value: V)?) | |
| -> Dictionary<K, V> | |
| { | |
| return array.reduce([:]) { | |
| (var dict, e) in | |
| if let (key, value) = transformer(element: e) | |
| { | |
| dict[key] = value | |
| } | |
| return dict | |
| } | |
| } | |
| struct Person | |
| { | |
| let name: String | |
| let age: Int | |
| } | |
| let people = [ | |
| Person(name: "Billy", age: 42), | |
| Person(name: "David", age: 24), | |
| Person(name: "Maria", age: 99)] | |
| let dictionary = toDictionary(people) { ($0.name, $0.age) } | |
| println(dictionary) | |
| // Prints: [Billy: 42, David: 24, Maria: 99] |
I don’t think we should be creating this kind of thing for specific structs and classes; instead let’s make this an instance method of a protocol, and extend Array to implement it, as with C#: http://msdn.microsoft.com/en-us/library/bb549277(v=vs.95).aspx
Let me know when you put together a sample of this, I’m curious to see your approach.