NSSortDescriptor评估递增数字（Swift） [英] NSSortDescriptor evaluating ascending numbers (Swift)

问题描述

应用程式已将 contentid 作为json档案中的数字字串输入：

App has contentid coming in as a number string from a json file:

let contentid: AnyObject! = jsonFeed["contentid"]

let stream:Dictionary = [
   "contentId": contentid as! String,
]

后来保存到[NSManagedObject]：

It is later saved to [NSManagedObject] with:

var articles = [NSManagedObject]()

let entity =  NSEntityDescription.entityForName("Article", inManagedObjectContext: managedContext)
let article = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedContext)

article.setValue(stream["contentId"], forKey: "contentid")

articles.append(article)

最后，我使用NSSortDescriptor让Core Data返回升序：

Finally, I use NSSortDescriptor to have Core Data return entries in numerical ascending order:

let sort = NSSortDescriptor(key: "contentid", ascending: true)
fetchRequest.sortDescriptors = [sort]

但条目 6 - 10 返回为： 10，6，7，8，9 。使用NSSortDescriptor正确计算这些数字的正确方法是什么？

But entries 6 - 10 are returned as: 10, 6, 7, 8, 9. What would be the correct method of having these numbers evaluated correctly using NSSortDescriptor?

UPDATE：

对于Swift版本，请参见下面的Volker的回答。我最后使用：

For the Swift version, please see Volker's answer below. I ended up using:

let sort = NSSortDescriptor(key: "contentid", ascending: true, selector: "localizedStandardCompare:")

，并将编号的字符串评估为真实整数。

and it evaluated the numbered strings as true integers.

UPDATE：Swift 2：

选择器语法已更改，不再接受objc指针。谢谢user1828845。

Selector syntax has changed and no longer accepts objc pointers. Thank you user1828845.

let sort = NSSortDescriptor（key：contentid，ascending：true，selector：#selector（NSString.localizedStandardCompare ：）））

推荐答案

你想要的值实际上是字符串，奇怪的排序顺序。对于Swift，存在 NSSortDescriptor 的初始化器 init（key：ascending：selector：），因此可以使用
selector：localizedStandardCompare：（如nshipster.com/nssortdescriptor

The values you want to sot are actually strings and not numbers, thus the strange sort order. For Swift there exist an initializer init(key:ascending:selector:) of NSSortDescriptorand thus you can use selector: "localizedStandardCompare:" as described for example at nshipster.com/nssortdescriptor

$ c> localizedStandardCompare：给你一个Finder像字符串值的排序，数字的排序方式，自然排序数字。所以1，...，9,10，...，99,100等。

The localizedStandardCompare: gives you a Finder like sorting of string values in a way that numbers are sorted naturally as you would sort numbers. So 1,...,9,10,...,99, 100 etc.

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