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在 C 中，将指针指向分配给指针的内存位置是有效的：

static void * SomeContext = &SomeContext;

通过将此指针用作 in ，我已经看到它在带有 KVO 的 Objective-C 代码库中context使用observeValueForKeyPath:ofObject:change:context:。

是否可以将指针指向 Swift 中为该指针分配的内存空间，或者手动为该指针分配内存？在初始化期间尝试将指针指向自身的内存值会导致错误（如预期的那样）：

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

CMutableVoidPointer该语言中不再存在，并且UnsafeMutablePointer<Void>()不推荐使用初始化指针 ( ) 并将指针设置为nil.

也许是这样的：

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<()>')
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1 回答 1

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在 Swift 3 上：

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

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

斯威夫特 2：

用于withUnsafePointer获取指向变量的指针。然后将其分配给自己。

var somePointer: UnsafeMutablePointer<Void> = nil
withUnsafePointer(&somePointer) { somePointer = UnsafeMutablePointer($0) }
于 2016-05-31T20:19:25.903 回答