Swift language: nil check, and if so instantiate new object

Question

Is there any way I can simplify this:

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

private func addToUnloadedImagesRow(row: Int, forLocation:String!) {
    if unloadedImagesRows[forLocation] == nil {
                    unloadedImagesRows[forLocation] = [Int]()
    }
    unloadedImagesRows[forLocation]!.append(row)
}

Doesn't Swift have an easy way to check for nil, and if so, create a new object, and all subsequent uses refers to the object?

Answer 1

You can simplify it into just one line:

private func addToUnloadedImagesRow(row: Int, forLocation:String!) {
    unloadedImagesRows[forLocation] = (unloadedImagesRows[forLocation] ?? []) + [row]
}

Answer 2

You can create a helper operator for nil checks and use it like below.

infix operator ?= { associativity left precedence 160 }

func ?=<T: Any>(inout left: T?, right: T) -> T {
    if let left = left {
        return left
    } else {
        left = right
        return left!
    }
}

Here you will be able to use it like unloadedImagesRows[forLocation] ?= [Int]() if empty

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

private func addToUnloadedImagesRow(row: Int, forLocation:String!) {
    unloadedImagesRows[forLocation] ?= [Int]()
    unloadedImagesRows[forLocation]!.append(row)
}

addToUnloadedImagesRow(1, forLocation: "This is something")

print(unloadedImagesRows) // "["This is something": [1]]\n"