Differences between [NSArray arrayWithArray:] and [NSArray copy]

Question

lately I work much with arrays and I\'m wonder.. what\'s diffrences between those two lines.

NSArray *array = [NSArray arrayWithArray:someArray];

Answer 1

In Swift, it's very different. Thanks to the new open-source Foundation for Swift, we know that whereas init(array:) creates a new array with the items given (if any), copy() simply returns self.

    public override func copy() -> AnyObject {
        return copyWithZone(nil)
    }

    public func copyWithZone(zone: NSZone) -> AnyObject {
        return self
    }

^{https://github.com/apple/swift-corelibs-foundation/blob/master/Foundation/NSArray.swift#L82}

    public convenience init(array: [AnyObject]) {
        self.init(array: array, copyItems: false)
    }

    public convenience init(array: [AnyObject], copyItems: Bool) {
        let optionalArray : [AnyObject?] =
            copyItems ?
                array.map { return Optional<AnyObject>(($0 as! NSObject).copy()) } :
                array.map { return Optional<AnyObject>($0) }

        // This would have been nice, but "initializer delegation cannot be nested in another expression"
//        optionalArray.withUnsafeBufferPointer { ptr in
//            self.init(objects: ptr.baseAddress, count: array.count)
//        }
        let cnt = array.count
        let buffer = UnsafeMutablePointer<AnyObject?>.alloc(cnt)
        buffer.initializeFrom(optionalArray)
        self.init(objects: buffer, count: cnt)
        buffer.destroy(cnt)
        buffer.dealloc(cnt)
    }

^{https://github.com/apple/swift-corelibs-foundation/blob/master/Foundation/NSArray.swift#L116}

So, obviously, copy() is faster, and now you know how they both work! _{(Just only in Swift)}