_ArrayType或_ArrayProtocol在Swift 3.1中不可用吗?

问题描述

在swift 2.1上运行时，我在项目中使用了_ArrayType.我上周升级到Swift 3.0.2(Xcode 8.2.1)，发现在这里将_ArrayType更改为_ArrayProtocol并且运行良好.

I was using _ArrayType in my project when I was running on swift 2.1. I upgraded to swift 3.0.2 (Xcode 8.2.1) last week and I found here that _ArrayType is changed to _ArrayProtocol and it was working well.

今天，我将Xcode升级到8.3.1，这给了我错误:Use of undeclared type '_ArrayProtocol'.这是我的代码:

Today I upgraded my Xcode to 8.3.1, and it gives me error:Use of undeclared type '_ArrayProtocol'. Here is my code:

extension _ArrayProtocol where Iterator.Element == UInt8 {
    static func stringValue(_ array: [UInt8]) -> String {
        return String(cString: array)
    }
}

现在怎么了?为什么_ArrayProtocol在swift 3.0.2.中工作时未在swift 3.1中声明.

What's wrong now? Why _ArrayProtocol is undeclared in swift 3.1 while it was working in swift 3.0.2.

另外，当我在这里查看在git中我看到_ArrayProtocol可用.比起我 Swift 2.1文档，我能够在协议列表中看到"_ArrayType"，但是在Swift中 3.0 / 3.1 文档我看不到_ArrayProtocol.

Also when I look here in git I see _ArrayProtocol available.Than I looked into Swift 2.1 docs I am able to see '_ArrayType' in protocol listing but in Swift 3.0/3.1 docs I am not able to see _ArrayProtocol.

推荐答案

以下划线开头的类型名称应始终视为内部名称.在Swift 3.1中，它在源代码中被标记为internal，因此不公开显示.

Type names starting with an underscore should always treated as internal.In Swift 3.1, it is marked as internal in the source code and thereforenot publicly visible.

在早期的Swift版本中，使用_ArrayProtocol是一种解决方法您无法定义具有相同类型"要求的Array扩展名.从Swift 3.1开始，这已经成为可能，如 Xcode 8.3发行说明:

Using _ArrayProtocol was a workaround in earlier Swift versions whereyou could not define an Array extension with a "same type" requirement.This is now possible as of Swift 3.1, as described in theXcode 8.3 release notes:

因此不再需要使用内部协议，您只需定义

Using the internal protocol is therefore not necessary anymore,and you can simply define

extension Array where Element == UInt8 {

}

但是请注意，您的static func stringValue()不需要任何元素类型的限制.您可能想要的是像这样定义 instance方法:

But note that your static func stringValue() does not need anyrestriction of the element type. What you perhaps intended is todefine an instance method like this:

extension Array where Element == UInt8 {

    func stringValue() -> String {
        return String(cString: self)
    }

}

print([65, 66, 67, 0].stringValue()) // ABC

还请注意，String(cString:)期望以 null终止的序列的UTF-8字节.

Also note that String(cString:) expects a null-terminated sequenceof UTF-8 bytes.

这篇关于_ArrayType或_ArrayProtocol在Swift 3.1中不可用吗?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！