Initializing an empty Dictionary - style question

Using Swift
#1

Hi, I was reading some Wenderlich tutorials and I noticed people like to initialize Dictionaries like so:

var skipTable: [Character: Int] = [:]

But I think it’s minutely easier to read:

var skipTable = [Character:Int]()

Is this just a style preference or is there a performance penalty here? Thanks.

#2

For all intents and purposes, they’re equivalent and simply a matter of style: https://godbolt.org/g/xnAZQy

I will point out though that there’s also the alternative

var skipTable = Dictionary<Character, Int>()

:wink:

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#3

i really don’t think either is superior but my personal style is to use

let dict:[T: T] = [:]

so that the type information lives on the left side of the assignment, just like any other Swift variable declaration. that’s also why i like to use

let buffer:UnsafeMutablePointer<Int> = .allocate(capacity: 13)

and

let foo:Foo = .init()
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#4

My reason for preferring var skipTable: [Character: Int] = [:] over the alternatives has to do with education and the order in which topics are introduced to programming students.

I am very strict about not using syntax or features a student hasn’t learned yet, and not introducing things too early. As such, I teach data structures fairly early on, after control flow and functions, but before custom types. The syntax above lets me do that, as it uses a literal instead of an initializer for initialization (unlike var skipTable = [Character:Int]()) and does not require generics (unlike var skipTable = Dictionary<Character, Int>()).

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