使用未声明的类型'AttributedString' [英] Use of undeclared type 'AttributedString'

问题描述

Xcode 8 beta 4不再识别基础类AttributedString.

Xcode 8 beta 4 no longer recognizes Foundation class AttributedString.

我已经在一个简单的游乐场示例中复制了它:

I've reproduced it in this simple playground example:

//: Playground - noun: a place where people can play

import Foundation

let attrStr1 = NSAttributedString()
let attrStr2 = AttributedString()  // Use of undeclared type 'AttributedString'

由于AttributedString在较早的Xcode 8 Swift 3 Beta中可用，所以我想这是需要修复的Foundation错误，而不是Playground中的某些源代码错误?

Since AttributedString was available in older Xcode 8 Swift 3 betas, I imagine this is a Foundation bug that needs to be fixed, rather than some source code error in Playground?

推荐答案

尽管Xcode发行说明中未记录，但Swift进化提案的版本2更新

Although undocumented in the Xcode release notes, a version 2 update to Swift evolution proposal SE-0086 Drop NS Prefix in Swift Foundation has added the "NS" prefix back to several Foundation classes which previously dropped the prefix.

原因如下:

如果计划在不久的将来使该类具有等效的值类型，则保留NS前缀.例如:NSAttributedString，NSRegularExpression，NSPredicate.

If the class is planned to have a value-type equivalent in the near future, then keep the NS prefix. Examples: NSAttributedString, NSRegularExpression, NSPredicate.

因此，Swift AttributedString类型将在 some 点返回，作为下一次结构，而不是作为类.

So, the Swift AttributedString type will return at some point, as a struct next time, instead of being a class.

听起来其中一些改进将成为"Swift 4的重点领域".目前，有必要恢复使用NSAttributedString类.

It sounds like some of these improvements will be "a focus area for Swift 4." For now, it's necessary to revert back to using the NSAttributedString class.

如果您想知道SE-0086 v2更新影响了多少种类型，看起来就像

If you're curious to know how many types were affected by the SE-0086 v2 update, it looks like the revision affects ~32 types which had previously dropped the NS prefix for Swift 3.

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