9 Nil Coalescing Operator in Swift
The nil-coalescing operator (a ?? b) unwraps an optional a if it contains a value, or returns a default value b if a is nil. The expression a is always of an optional type. The expression b must match the type that’s stored inside a.
The nil-coalescing operator is shorthand for the code below:
a != nil ? a! : b
The code above uses the ternary conditional operator and forced unwrapping (a!) to access the value wrapped inside a when a isn’t nil, and to return b otherwise. The nil-coalescing operator provides a more elegant way to encapsulate this conditional checking and unwrapping in a concise and readable form.
https://docs.swift.org/swift-book/Lan...