??= An operator that will assign the left hand value to the right hand value if the left hand value is nil

assign-if-nil.swift

/**

    ??= An operator that will assign the left hand value
    to the right hand value if the left hand value is nil

    Example Usage:

    ```
    var str: String?
    str ??= "Bob"
    print(str!)
    ```
 
     - TODO: Define a precedence group
 
 */

import UIKit

infix operator ??=

func ??=(lhs: inout String?, rhs: String) {
    if lhs == nil {
        lhs = rhs
    }
}