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up vote 0 down vote favorite

I'm creating my base models in Swift(2.0) and then controlling the views in Objective-C. I'm still new to Swift, so hopefully I'm just overlooking something simple, but here is the problem:

I’m making a mutable array in Swift, but when I initialize the array in my Objective-c portion of the program, it becomes an NSArray, more specifically it becomes: Swift._SwiftDeferredNSArray

Why is it becoming immutable when I initialize? Here’s my swift code:

import Foundation

@objc public class Model : NSObject {

    var books:[Book]

    override init(){
        self.books = [Book]()
    }

}

And here’s my Obj-c Code; 

Model *bookCollection = [[Model alloc]init];

I’m unable to add objects to my bookCollection.books array (because it has become an NSArray) and when I set a breakpoint and po it, I can see that it is a "Swift._SwiftDeferredNSArray”. bookCollection.books is supposed to be an NSMutableArray.

Any thoughts?

share|improve this question
    
Try putting the dynamic keyword in front of the books declaration. –  Qbyte 4 hours ago
    
Just tried dynamic var books:[Book] , unfortunately it didn't change anything. –  Alan_s 4 hours ago

2 Answers 2

up vote 1 down vote accepted

In swift, the difference between mutable and immutable array is;

var books:[Book] // is a mutable array
let books:[Book] = [book1, book2]; // is immutable array due to let

but I don't think, same rule is followed when bridging to ObjC.

Just for a fix, you may have mutableArray specifically. 

import Foundation

@objc public class Model : NSObject {

    var books:NSMutableArray = NSMutableArray();

    override init(){
        super.init();
        // other code
    }

}

You will need to parse the values to Book Class when retrieving from the array.

share|improve this answer
    
Thank you! I'll mark this as the correct answer but is this the correct way to initialize my array in Swift in the ovverride init method: self.books = [] Or is there a more proper way? –  Alan_s 3 hours ago
    
There is an option to initialize it with it's definition as I did but I do not see any issue if you initialize the same in your init(). –  Shoaib 3 hours ago
up vote 1 down vote

bookCollection.books is supposed to be an NSMutableArray.

No, it is not. Var does not mean that the bridged Objective-C object is to be mutable: it means that the property can be assigned to.

The Swift array type is a structure, not a class. This has important bridging implications. The reference itself cannot be shared without passing it as an inout value, and even then the references cannot be stored. If it bridged as a NSMutableArray, it would be possible to have undetectable mutating references, and Swift does not allow that.

You should be able to assign a new NSArray to your property from Objective-C code, though. For instance, this should work:

bookCollection.books = [bookCollection.books arrayByAddingObject:myNewBook];

Your other option, obviously, is to declare books as a NSMutableArray from the Swift side.

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