更新类型Int32的CoreData属性 [英] Update CoreData attribute of type Int32

问题描述

我想获取核心数据属性的值，在获取此对象/值后，我想更新它。这是我的代码：

I'd like to get the value of an core data attribute and after getting this object/value I'd like to update it. This is my code:

var numberOfChanges:Int32?
numberOfChanges = theme.valueForKey("numberThemeChanged") as Int32
var newValueThemeChanges:Int32?
newValueThemeChanges = numberOfChanges+1
theme.setValue(newValueThemeChanges, forKey: "numberThemeChanged")

$ b b

我收到以下错误：

I'm getting the following errors:

1. 类型Int32不符合协议'在此行代码中的： numberOfChanges = theme.valueForKey（numberThemeChanged）as Int32 。


2. 'Int32'不等于这行代码中的'AnyObject'： theme.setValue（newValueThemeChanges，forKey：numberThemeChanged）



1. Type 'Int32' does not conform to protocol 'AnyObject' in this line of code: numberOfChanges = theme.valueForKey("numberThemeChanged") as Int32.
2. 'Int32' is not identical to 'AnyObject' in this line of code: theme.setValue(newValueThemeChanges, forKey: "numberThemeChanged")

你知道我怎么做/我的代码出了什么问题？
感谢您的回答！

Do you know how I can do it/what's wrong with my code? Thanks for your answer!

推荐答案

键值编码方法

func valueForKey(key: String) -> AnyObject?
func setValue(value: AnyObject?, forKey key: String)

类型 AnyObject ，对于整数属性，这些
是 NSNumber 的实例。

work with values of the type AnyObject, for an integer attribute these are instances of NSNumber.

Int 和 NSNumber 之间有一个自动桥接，但不是
之间的 Int32 和 NSNumber （这与
无关的事实，你定义的属性作为核心数据
模型检查器中的整数32）。

There is an automatic bridging between Int and NSNumber, but not between Int32 and NSNumber (and this has nothing to do with the fact that you define the property as "Integer 32" in the Core Data model inspector).

您有几个选项：

• 只需使用类型 Int 的变量：

var numChanges = theme.valueForKey("numberThemeChanged") as Int
numChanges++
theme.setValue(numChanges, forKey: "numberThemeChanged")

使用 Int32 ，并从和转换为 NSNumber 显示：

Use Int32 and convert from and to NSNumber explicitly:

var numberOfChanges = (theme.valueForKey("numberThemeChanged") as NSNumber).intValue // Int32
numberOfChanges++
theme.setValue(NSNumber(int: numberOfChanges), forKey: "numberThemeChanged")

使用Xcode - >编辑器 - >创建NSManagedObject子类...并选中为原始数据类型使用标量属性选项。
这将给你一个带有属性的托管对象子类。

Use Xcode -> Editor -> Create NSManagedObject subclass ... and check the "Use scalar properties for primitive data types" options. This will give you a managed object subclass with the property

@NSManaged var numberThemeChanged: Int32

，您可以访问该属性而不使用键值编码：

and you can access the property without Key-Value Coding:

var numberOfChanges = theme.numberThemeChanged
numberOfChanges++
theme.numberThemeChanged = numberOfChanges

li>

下面是一个完整的创建或更新示例：

Here is a complete "create-or-update" example:

var theme : Entity!

let request = NSFetchRequest(entityName: "Entity")
var error : NSError?
if let result = context.executeFetchRequest(request, error: &error) as [Entity]? {
    if result.count > 0 {
        // (At least) one object found, set `theme` to the first one:
        theme = result.first!
    } else {
        // No object found, create a new one:
        theme = NSEntityDescription.insertNewObjectForEntityForName("Entity", inManagedObjectContext: context) as Entity
        // Set an initial value:
        theme.setValue(0, forKey: "numberThemeChanged")
    }
} else {
    println("Fetch failed: \(error?.localizedDescription)")
}

// Get value and update value:
var numChanges = theme.valueForKey("numberThemeChanged") as Int
numChanges++
theme.setValue(numChanges, forKey: "numberThemeChanged")

// Save context:
if !context.save(&error) {
    println("Save failed: \(error?.localizedDescription)")
}

println(numChanges)

这篇关于更新类型Int32的CoreData属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！