ios 如何设置和获取指针 Swift 的值
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How to set & get value of pointer Swift
提问by Giang
In Objetive-C when I want set/change value of pointer. I use
在 Objetive-C 中，当我想设置/更改指针值时。我用
*pointer = value
But In Swift, how to get/set value of pointer?
但是在 Swift 中，如何获取/设置指针的值？
I'm woking with bitmap pixel:
我正在使用位图像素：
NSUInteger offsetPixelCountForInput = ghostOrigin.y * inputWidth + ghostOrigin.x;
for (NSUInteger j = 0; j < ghostSize.height; j++) {
for (NSUInteger i = 0; i < ghostSize.width; i++) {
UInt32 * inputPixel = inputPixels + j * inputWidth + i + offsetPixelCountForInput;
UInt32 inputColor = *inputPixel;
newR = MAX(0,MIN(255, newR));
newG = MAX(0,MIN(255, newG));
newB = MAX(0,MIN(255, newB));
*inputPixel = RGBAMake(newR, newG, newB, A(inputColor));
}
}
So I want to convert this code into Swift, but I'm stuck with pointers.
所以我想把这段代码转换成 Swift，但我被指针困住了。
23.03.2016 - Update code
23.03.2016 - 更新代码
var inputPixels:UnsafeMutablePointer<UInt32> = nil
inputPixels = UnsafeMutablePointer<UInt32>(calloc(inputHeight * inputWidth, UInt(sizeof(UInt32))))
回答by Kostiantyn Koval
You can work with pointers in Swift. There are UnsafePointerand UnsafeMutablePointergeneric types.
您可以在 Swift 中使用指针。有UnsafePointer和UnsafeMutablePointer泛型类型。
Here is a function that takes a floatpointer
You can use float variable and pass it's address &floatVar
or you can create and allocate an UnsafeMutablePointerand pass it. But you have to manually allocate and deallocate memory.
这是一个带有float指针的函数
您可以使用浮点变量并传递它的地址，&floatVar
或者您可以创建并分配一个UnsafeMutablePointer并传递它。但是您必须手动分配和释放内存。
When you work with an UnsafeMutablePointerpointer type and want to assign some value to it you have to do the following:
当您使用UnsafeMutablePointer指针类型并希望为其分配一些值时，您必须执行以下操作：
- check if points to some variable (not nil)
- Assign your value to the
memoryproperty
- 检查是否指向某个变量（非零）
- 将您的价值分配给该
memory物业
Code Example:
代码示例：
func work (p: UnsafeMutablePointer<Float>) {
if p != nil {
p.memory = 10
}
println(p)
println(p.memory)
}
var f: Float = 0.0
var fPointer: UnsafeMutablePointer<Float> = UnsafeMutablePointer.alloc(1)
work(&f)
work(fPointer)
fPointer.dealloc(1)
回答by Roman
You should use pointeeproperty instead of memoryin Swift 3
您应该在 Swift 3 中使用指针属性而不是内存
pointer.pointee = value
