UnsafePointer 不再适用于 swift 3

Posted 2023-02-24

【中文标题】UnsafePointer 不再适用于 swift 3

【英文标题】：UnsafePointer no longer works in swift 3

【发布时间】：2016-10-03 03:47:26

【问题描述】：

我从 swift 2 转换为 swift 3 后，下面提到的行弹出错误

let value = UnsafePointer<UInt32>(array1).pointee

“init”不可用：使用“withMemoryRebound(to:capacity:_)”临时将内存视为另一种布局兼容类型。

在 swift2 中是这样的

let value = UnsafePointer<UInt32>(array1).memory

有人可以解释一下吗？ 抱歉，我对 swift3 很陌生

修改后

let abc = UnsafePointer<UInt32>(array1).withMemoryRebound(to: <#T##T.Type#>, capacity: <#T##Int#>, <#T##body: (UnsafeMutablePointer<T>) throws -> Result##(UnsafeMutablePointer<T>) throws -> Result#>)

但仍然应该将什么值放入变量中？对不起，我已经搜索了但是太糟糕了我找不到解决方案

【问题讨论】：

Results from C functions that return nullable pointers must be explicitly unwrapped before accessing the pointee property (formerly memory) or subscript elements. Optional chaining syntax works well here, e.g. result?.pointee = sum. 可能会有所帮助...swift.org/migration-guide

请展示你真正想要做什么。

array1是什么类型的？UnsafeRawPointer？

@LinShiwei var array1 = [UInt8](count4: 重复 0)

【参考方案1】：

你可以试试这个：

let rawPointer = UnsafeRawPointer(array1)
let pointer = rawPointer.assumingMemoryBound(to: UInt32.self)
let value = pointer.pointee

原始指针是用于访问非类型数据的指针。

assumingMemoryBound(to:) 可以从UnsafeRawPointer 转换为UnsafePointer<T>。

参考：Swift 3.0 Unsafe World

【参考方案2】：

如果array 是Array，最好使用withUnsafeBufferPointer：

array.withUnsafeBufferPointer  buffer in
    // do something with 'buffer'
    // (if you need an UnsafePointer rather than an UnsafeBufferPointer,
    // you can access that via the buffer's .baseAddress property)

确保不要让缓冲区指针从闭包中逃逸，因为它在闭包之外无效。