EXC_BAD_INSTRUCTION object array assign Swift

I have an array of Printable objects, but I need them Equatable and AnyObject compliant.

private(set) var items: [Printable] = []

class func withItems<T: AnyObject where T: Equatable, T: Printable>(items: [T], selectedItem: T? = nil) {
   ... instance init ...
   instance.items = items
}

And it result on EXC_BAD_INSTRUCTION:

fatal error: array cannot be bridged from Objective-C

This is one try to this problems:

• Generic function and attribute with Equatable and Printable as parameters in Swift

why?

A Swift Array must contain all one kind of object (e.g. all String or all Int). An Objective-C NSArray can contain many different kinds of objects (e.g. some NSStrings and some NSNumbers). Hence if you get that kind of array from Objective-C you can't magically assign it into a Swift array reference.

What I do in that situation is munge the array to make it acceptable to Swift. I don't know what the details are of what you're getting back from Objective-C; your actual strategy will depend on those details and what you want to do with the array. One approach is to assign / cast into a Swift array of AnyObject. Or you might decide to leave it as an NSArray and work with it entirely through NSArray methods.

Here's an example from my own code. arr is an NSArray that's a mixed bag of NSString and NSNull objects. I know none of the NSString objects are the empty string, so I substitute the empty string for all the NSNull objects, thus giving me an array of just strings, which Swift can deal with:

let arr2 = (arr as Array).map { $0 as? String ?? "" }

Now arr2 is a pure Swift [String] array.