How to append to an array that is a value in a Swift dictionary

Question

Let\'s assume I have a dictionary that accepts a string as the key and an array as value:

var d = [String: [Int]]()
d[\"k\"] = [Int]()

Now I wo

Answer 1

All other answers are correct, but If you feel annoying to check nil, unwrap ...

I made a custom operator.

With this, you can unconditionally expand Optional arrays

infix operator +=! {
    associativity right
    precedence 90
    assignment
}

func +=!(inout lhs:[T]?, rhs:S) {
    if lhs == nil {
        // the target is `nil`, create a new array
        lhs = Array(rhs)
    }
    else {
        // the target is not `nil`, just expand it
        lhs! += rhs
    }
}

Usage:

var d = [String: [Int]]()

// ... d["test"] may or may not exists ...

d["test"] +=! [1]