在swift中将self转换成UnsafeMutablePointer<Void>

对象指针可以被转化为UnsafePointer<Void>，同时也可以被转化回来。在OC中，可能是这样

void *voidPtr = (__bridge void*)self;
MyType *mySelf = (__bridge MyType*)voidPtr;

Swift中有个Unmanaged可以完成这个需求。因为它是使用COpaquePointer来替代UnsafePointer<Void>的，所以使用起来可能有些麻烦。

func bridge<T: AnyObject>(obj: T) -> UnsafePointer<Void> {
	return UnsafePointer(Unmanaged.passUnretained(obj).toOpaque())
}

func bridge<T: AnyObject>(prt: UnsafePointer<Void>) -> T {
	return Unmanaged<T>.fromOpaque(COpaquePointer(ptr).takeUnretainedValue()
}

这种复杂的表达只是为了满足Swift严格的类型系统。在编译时，这仅仅是为了转换两个指针的类型而已。也可以使用将self传递进来

let voidPtr = bridge(self)

或者使用`UnsafeMutablePointer(bridge(self)).

也可以转换回对象指针

let mySelf: MyType = bridge(voidPtr)

另外，OC中的__bridge_retained和__bridge_transfer，在Swift中也可以用下面的代码表示

func bridgeRetained<T: AnyObject>(obj: T) -> UnsafePointer<Void> {
	return UnsafePointer(Unmanaged.passRetained(obj).toOpaque())
}

func bridgeTransfer<T: AnyObject>(ptr: UnsafePointer<Void>) -> UnsafePointer<Void> {
	return Unmanaged<T>.fromOpaque(COpaquePointer(ptr)).takeRetainedValue()
}

原文链接：[How to cast self to UnsafeMutablePointer type in swift](http://stackoverflow.com/questions/33294620/how-to-cast-self-to-unsafemutablepointervoid-type-in-swift)

在swift中将self转换成UnsafeMutablePointer

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