How can I initialize a generic mutable array in Swift?

Question

I tried this:

var ss: [S] = NSMutableArray<S>(capacity: 0)

Compiler says: Cannot specialize non-generic type 'NSMutableArray'

Why?

Antonio · Accepted Answer · 2014-08-26 14:49:05Z

23

NSArray and NSMutableArray are Objective C types, and do not support generics. You can instantiate as swift's native array type:

var settings = [Setting]()

which also can be written as

var settings = Array<Setting>()

Thanks to type inference, you don't have to specify the type, but if you like this are the complete versions:

var settings: [Setting] = [Setting]()
var settings: Array<Setting> = Array<Setting>()

Note that [Setting] and Array<Setting> are interchangeable, meaning they define the same object type, so you can use whichever you like more.

answered Aug 26, 2014 at 14:49

Antonio

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6 Comments

János Over a year ago

do you know how can I add elements from an NSOrderedSet to settings?

Antonio Over a year ago

If not wrong NSOrderedSet has an array property of NSArray type. In order to take advantage of swift generics, you have to loop though that array, cast each element to Setting and add to the settings array

János Over a year ago

I was able to add sequences also with += array generic operator

Antonio Over a year ago

Good to know. I didn't know it was possible. Thanks for sharing that :)

Radek Wilczak Over a year ago

You can use NSArray with generics in Objective-C! useyourloaf.com/blog/using-objective-c-lightweight-generics

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