ios 在 Swift 3 中使用 NSNumber 和整数值

Working with NSNumber & Integer values in Swift 3

提问by A.Roe

I am trying to convert my project to Swift 3.0 however I am having two error messages when working with NSNumberand Integers.

我正在尝试将我的项目转换为 Swift 3.0，但是在使用NSNumber和时出现两条错误消息Integers。

Cannot assign type int to type NSNumber

无法将类型 int 分配给类型 NSNumber

for

为了

//item is a NSManaged object with a property called index of type NSNumber 

var currentIndex = 0
 for item in self.selectedObject.arrayOfItems {
   item.index = currentIndex
   currentIndex += 1
 }

and even when I change currentIndexto a type NSNumberthen I get the error

甚至当我更改currentIndex为一种类型时，我也会NSNumber收到错误消息

Binary operator '+=' cannot be applied to type 'NSNumber' and 'Int'

二元运算符“+=”不能应用于类型“NSNumber”和“Int”

so then I create a property called oneof type NSNumberto add to currentIndexbut then get the following error;

所以然后我创建了一个名为onetype的属性NSNumber来添加，currentIndex但随后出现以下错误；

Binary operator '+=' cannot be applied to two NSNumber operands

二元运算符“+=”不能应用于两个 NSNumber 操作数

&& the second error I get is

&& 我得到的第二个错误是

No '+' candidates produce the expected contextual result type NSNumber

没有“+”候选产生预期的上下文结果类型 NSNumber

 let num: Int = 210
 let num2: Int = item.points.intValue
 item.points = num + num2

Here I am just trying to add 210 to the points property value, itemis a NSManagedObject.

在这里，我只是想将 210 添加到 points 属性值，item是一个NSManagedObject.

So basically I am having issues getting my head around adding numbers to properties of type NSNumber. I am working with NSNumberbecause they are properties of NSManagedObject's.

所以基本上我在为 type 的属性添加数字时遇到了问题NSNumber。我正在使用，NSNumber因为它们是NSManagedObject's 的属性。

Can anyone help me out ? I have over 80 errors which are all either one of the above errors mentioned.

谁能帮我吗 ？我有 80 多个错误，它们都是上述错误之一。

Thanks

谢谢

回答by Martin R

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

在 Swift 3 之前，许多类型会NSObject在必要时自动“桥接”到某个子类的实例，例如Stringto NSString, or Int, Float, ... to NSNumber。

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

从 Swift 3 开始，您必须明确转换：

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 NSManagedObjectsubclass, then the property has some integer type instead of NSNumber, so that you can get and set it without conversion.

或者，在创建NSManagedObject子类时使用选项“为原始数据类型使用标量属性” ，然后该属性具有一些整数类型而不是NSNumber，以便您无需转换即可获取和设置它。

回答by danieltmbr

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

在 Swift 4 中（在 Swift 3 中可能相同）NSNumber(integer: Int)被替换为NSNumber(value: )wherevalue几乎可以是任何类型的数字：

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)

回答by Hamed Ghadirian

Swift 4:

斯威夫特 4：

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

回答by jboi

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

您应该保留或原始代码并更改分配，以便它工作：

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.

由于您的代码在 Swift 2 中运行良好，我预计这种行为可能会在下一次更新中发生变化。

回答by FuatK

Swift 4.2

斯威夫特 4.2

item.index = Int(truncating: currentIndex)