CODEWITHSUNDEEP
swiftswift2named-parameters
fiship
fiship

Reputation: 15

Swift: Why no labeled arguments in this situation?

For this code

let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as! NSString

I will have forgot what the third argument stands for, soon.

For some reason Swift (2.0) doesn't allow me to label the arguments like that:

let documentsPath = NSSearchPathForDirectoriesInDomains(directory: .DocumentDirectory,
domainMask: .UserDomainMask, expandTilde: true)[0] as! NSString  // error

I really hope I'm missing something!
Or rather: I really hope I don't have to miss the single best feature from Objective-C.

Upvotes: 1

Views: 110

Answers (1)

Duncan C
Duncan C

Reputation: 131491

It has to do with the way the function is defined. If it isn't defined with named arguments, you can't call it with named arguments.

NSSearchPathForDirectoriesInDomains is either a C style function (not a method) or a compiler macro that generates inline code. (It looks to me like it's a C function.) Neither of those accept named arguments, so you can't.

If you really want to stay away from unnamed arguments, create a utilities class that provides glue code that accepts named arguments and then calls the function in question. That way you encapsulate the old-style code in only one place. There will be a (tiny) performance cost to the extra function call, but in nearly all cases it will be unnoticeable.

Upvotes: 3

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