Double question mark is a nil-coalescing operator . In plain terms, it is just a shorthand for saying != nil . First it checks if the the return value is nil, if it is indeed nil, then the left value is presented, and if it is nil then the right value is presented.
Read moreWhat are optionals in Swift?
An Optional is a type on its own, actually one of Swift 4’s new super-powered enums . It has two possible values, None and Some(T), where T is an associated value of the correct data type available in Swift 4.
Read moreWhat does += mean in Swift?
The expression a += 2 is shorthand for a = a + 2 . Effectively, the addition and the assignment are combined into one operator that performs both tasks at the same time . Note. The compound assignment operators don’t return a value. For example, you can’t write let b = a += 2 .
Read moreWhat is _ variable in Swift?
Variables are used to store data in memory so that we can use them in program . Variables are like container that can hold data which can be changed later. Every variable has a unique name called identifier.
Read moreWhat is _ in Swift function parameter?
Omitting Argument Labels If you don’t want an argument label for a parameter, write an underscore ( _ ) instead of an explicit argument label for that parameter. // refer to the argument values for the first and second parameters.
Read moreWhat does _: mean in Swift documentation?
In the documentation it is being used as a wildcard to indicate a function that takes an unnamed parameter .
Read moreWhy do we use _ in Swift?
The _ is a placeholder for the parameter name . In your example, you call them differently, in the second function, you need to write the parameter name a: 1 . Swift’s function name convention is funcName(param1:param2:) , and it needs the _ as a placeholder to create the name of the function.
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