Working with NSNumber & Integer values in Swift 3

In Swift 4 (and it might be the same in Swift 3) NSNumber(integer: Int) was replaced with NSNumber(value: ) where value can be any almost any type of number:

public init(value: Int8)

public init(value: UInt8)

public init(value: Int16)

public init(value: UInt16)

public init(value: Int32)

public init(value: UInt32)


public init(value: Int64)

public init(value: UInt64)

public init(value: Float)

public init(value: Double)

public init(value: Bool)

@available(iOS 2.0, *)
public init(value: Int)

@available(iOS 2.0, *)
public init(value: UInt)

Swift 4:

var currentIndex:Int = 0
for item in self.selectedFolder.arrayOfTasks {
   item.index = NSNumber(value: currentIndex) // <--
   currentIndex += 1
}

Before Swift 3, many types were automatically "bridged" to an instance of some NSObject subclass where necessary, such as String to NSString, or Int, Float, ... to NSNumber.

As of Swift 3 you have to make that conversion explicit:

var currentIndex = 0
for item in self.selectedFolder.arrayOfTasks {
   item.index = currentIndex as NSNumber // <--
   currentIndex += 1
}

Alternatively, use the option "Use scalar properties for primitive data types" when creating the NSManagedObject subclass, then the property has some integer type instead of NSNumber, so that you can get and set it without conversion.

You should stay with or original code and just change the assignment, so that it works:

var currentIndex = 0
for item in self.selectedFolder.arrayOfTasks {
    item.index = NSNumber(integer: currentIndex)
    currentIndex += 1
}

As your code works fine in Swift 2, I'd expect that this is behaviour that might change in the next update.