Krischu
(Christoph K)
1
Consider the following piece of code from AppDelegate.swift:
func application(_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions:
[UIApplication.LaunchOptionsKey: Any]?) -> Bool
Just trying to understand and learn the language.
nuclearace
(Erik Little)
2
It's not so much the [] as [:] in this case. This is just one form of declaring a dictionary type.
let dict: [String: Int] = ["Hello": 2]
let dict2: Dictionary<String, Int> = dict
Krischu
(Christoph K)
3
Ah, thanks. I see. Swift has a slight resemblance with Python what the array, dictionary and tuple syntax is concerned.
On the other hand there is the square bracket nomenclature of Objective-C it could be intermixed with.
Anyway, it's got the syntax of its own. 
nuclearace
(Erik Little)
4
As an aside, although it's probably a bit much for a newcomer, Swift actually lets you make your own types become expressible by the different literals.
For example:
struct MyCustomType: ExpressibleByDictionaryLiteral {
init(dictionaryLiteral elements: (String, Int)...) {
}
}
func doesSomething(_ x: MyCustomType) { }
doesSomething(["hello": 1])
Just something to be aware of if you ever see a literal being passed to something that doesn't take the normal literal type.
[SomeType] is syntactic sugar for the type Array<SomeType>.
[TypeA: TypeB] is syntactic sugar for the type Dictionary<TypeA, TypeB>.
