點的UnsafeMutablePointer <Void>到本身

在C中，它是有效的，以有一個指針指向分配給指針的內存位置：點的UnsafeMutablePointer <Void>到本身

static void * SomeContext = &SomeContext;

我看這通過利用用於在目標C的代碼庫與KVO這個指針在observeValueForKeyPath:ofObject:change:context:中的context。

是否可以指向Swift中爲該指針分配的內存空間的指針，或者爲指針手動分配內存？試圖將指針指向初始化過程中本身的內存值導致錯誤（如預期）：

var somePointer: UnsafeMutablePointer<Void> = &somePointer // Error: Variable used within its own initial value

CMutableVoidPointer不會在語言存在了，並且初始化指針（UnsafeMutablePointer<Void>()）已被棄用，只是套指向nil。

也許是這樣的：

var ptr = malloc(sizeof(UnsafeMutablePointer<Void>)) 
ptr = &ptr // Error: error: cannot assign value of type 'inout UnsafeMutablePointer<Void>' (aka 'inout UnsafeMutablePointer<()>') to type 'UnsafeMutablePointer<Void>' (aka 'UnsafeMutablePointer<()>')

來源

2016-05-31 JAL

你想要達到什麼目的？ – Alexander

@AMomchilov你會如何在Swift中編寫'static void * SomeContext =＆SomeContext;'。這不是更大的問題的一部分，我只是想了解C指針如何橋接Swift工作。 – JAL

我應該知道你回答了這樣的問題，謝謝@MartinR。 – JAL

在

夫特3：

var somePointer = UnsafeMutableRawPointer(bitPattern: 1)! 
somePointer = UnsafeMutableRawPointer(mutating: &somePointer) 

print(somePointer) 
print(somePointer.load(as: UnsafeMutableRawPointer.self)) 
// Output of both should be the same.

夫特2：

Use withUnsafePointer獲取指針的變量。然後將其分配給自己。

var somePointer: UnsafeMutablePointer<Void> = nil 
withUnsafePointer(&somePointer) { somePointer = UnsafeMutablePointer($0) }

來源

2016-05-31 20:19:25 kennytm

點的UnsafeMutablePointer <Void>到本身

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