SKOOP SKOOP - 7 months ago 33
Swift Question

Changes in terminology for Swift function parameter labels

Swift provides the ability to give both an internal and external name/label for parameters of functions. But lately Apple seems to have resorted to only saying "Argument" and "Parameter" names/labels and dropped the use of internal/external to describe these things.

In the Swift documents, and WWDC videos, there are a few unclear efforts to describe the difference between a function's parameters and arguments, without referring to these as the outward facing or internal, such as:

Each function parameter has both an argument label and a parameter
name. The argument label is used when calling the function; each
argument is written in the function call with its argument label
before it. The parameter name is used in the implementation of the
function. By default, parameters use their parameter name as their
argument label.

Imagine a

Internally, the names of "when" and "height" might be different, and these are the internal names. External and internal don't seem to be at all confusing, other than the ordering in the Function Definition and then Declaration:

func jump(_ who: String, whenToJump when: Float, howHigh height: Int){
// wait for whenToJump
// adjust who.y by howHigh

Which of these is a parameter, in the sense Apple is referring to them, and which is an argument?


Everything is described in detail in the section Function Argument Labels and Parameter Names

in The Swift Programming Language (Swift 3)

Briefly, the differences between Swift 2 and Swift 3 are

  • "External name" (Swift 2) is now "Function Argument Label" (Swift 3)
  • "Internal name" (Swift 2) is now "Parameter Name" (Swift 3)
  • In (Swift 2) the first parameter is _ name (internal, but no external) by default
  • In (Swift 3) the first parameter is name name (function argument label and parameter name) by default.