How to get function's parameter value without parameter name in swift?-CodePudding

func test(_: [Int]) {
  print("xxx")
}

test([1,2,3])

I saw this code is valid in swift, how can I get the value passed into test?

CodePudding user response：

To explicitly answer your question:

how can I get the value passed in test?

You can't, in the same way that after

let _ = someFunction()

you have no way to get at the return value of someFunction. That's really the whole point of _ which basically means "I'm ignoring this intentionally".

CodePudding user response：

In order to get the parameter value inside the function, you have to specify the parameterName. Swift's function has this kind of structure :

func someFunction(argumentLabel parameterName: Int) {
    // In the function body, parameterName refers to the argument value
    // for that parameter.
}

where argumentLabel is used on the function caller, for example

func eat(byWhom person: String){}

would become

eat(byWhom: "Victor")

in the caller code. On the other hand, you can get the "Victor" value from the parameterName :

func eat(byWhom person: String){
    print(person) // should print "Victor"
}

CodePudding user response：

create function like this

func test(_ value: [Int]) { }

and then you can call it like this.

test([1,2]) without mentioning the parameter name.

CodePudding user response：

There's no chance to get functions parameter value w/o its name. That is why it is being used. But you can do this:

func test(_ value: [Int]) {
  print(value)
}


test([1,2,3])