Swift UnsafeMutablePointer & UnsafeMutablePointer<UnsafePointer<SomeType>>

Question

我正在尝试使用NSView的getRectsBeingDrawn，我不太确定如何转换它所需要的vars。

它的定义是：

func getRectsBeingDrawn(rects: UnsafeMutablePointer<UnsafePointer<NSRect>>, count: UnsafeMutablePointer<Int>)

我将rects和count定义为：

var rects: UnsafeMutablePointer<UnsafePointer<NSRect>> = nil            
var count: UnsafeMutablePointer<Int> = nil

这似乎很管用。调试器没有提供任何方便的方法来查看指针上的内容，所以这没有帮助。

rect应该在调用NSRect之后指向getRectsBeingDrawn数组，但它似乎没有返回任何内容。此外，我如何得到数组和int，其中的直肠和计数是指向的？

我正试图从苹果的示例"TableViewPlayground“中得到一段代码，以便快速工作。

- (void)drawSelectionInRect:(NSRect)dirtyRect {
    NSColor *primaryColor = [[NSColor alternateSelectedControlColor] colorWithAlphaComponent:0.5];
    NSColor *secondarySelectedControlColor = [[NSColor secondarySelectedControlColor] colorWithAlphaComponent:0.5];

// Implement our own custom alpha drawing
    switch (self.selectionHighlightStyle) {
        case NSTableViewSelectionHighlightStyleRegular: {
            if (self.selected) {
                if (self.emphasized) {
                    [primaryColor set];
                } else { 
                    [secondarySelectedControlColor set];
                }
                NSRect bounds = self.bounds;
                const NSRect *rects = NULL;
                NSInteger count = 0;
                [self getRectsBeingDrawn:&rects count:&count];
                for (NSInteger i = 0; i < count; i++) {
                    NSRect rect = NSIntersectionRect(bounds, rects[i]);
                    NSRectFillUsingOperation(rect, NSCompositeSourceOver);
                }
            }
            break;
        }
        default: {
            // Do super's drawing
            [super drawSelectionInRect:dirtyRect];
            break;
        }
    }
}

Answer 1

我设法把这事解决了..。我没有为rects和count正确分配内存

我所拥有的是：

var rects: UnsafeMutablePointer<UnsafePointer<NSRect>> = nil
var count: UnsafeMutablePointer<Int> = nil

最终解决这一问题的是：

var rects: UnsafeMutablePointer<UnsafePointer<NSRect>> = UnsafeMutablePointer<UnsafePointer<NSRect>>.alloc(1)
var count: UnsafeMutablePointer<Int> = UnsafeMutablePointer<Int>.alloc(1)

希望这能帮助其他人:)

如果有人感兴趣，请编辑，下面是上面的快速代码：

override func drawSelectionInRect(dirtyRect: NSRect) {
    var primaryColor = NSColor.alternateSelectedControlColor().colorWithAlphaComponent(0.5)
    var secondarySelectedControlColor = NSColor.secondarySelectedControlColor().colorWithAlphaComponent(0.5)

    switch (self.selectionHighlightStyle){
    case .Regular:
        if (self.selected){
            if self.emphasized{
                primaryColor.set()
            }else{
                secondarySelectedControlColor.set()
            }
            let bounds = self.bounds

            var rects: UnsafeMutablePointer<UnsafePointer<NSRect>> = UnsafeMutablePointer<UnsafePointer<NSRect>>.alloc(1)
            var count: UnsafeMutablePointer<Int> = UnsafeMutablePointer<Int>.alloc(1)

            self.getRectsBeingDrawn(rects, count: count)

            let rectArrayPtr = UnsafeMutableBufferPointer(start: rects, count: count.memory)
            var base = rectArrayPtr.baseAddress

            for var i = 0; i < count.memory; i++ {
                var currentRect = base.memory
                let rect = NSIntersectionRect(bounds, currentRect.memory)
                NSRectFillUsingOperation(rect, .CompositeSourceOver)
                base.successor()
            }

        }
    default:
            super.drawSelectionInRect(dirtyRect)
        }
}

编辑

根据另一项评论，在这里也采用了一种不那么冗长的方法(多亏了下面的Paul Patterson )：

http://stackoverflow.com/questions/32536855/using-getrectsbeingdrawn-with-swift