Swift UnsafeMutablePointer & UnsafeMutablePointer>

Question

我正在尝试使用 NSView 的 getRectsBeingDrawn，但我不太确定如何转换它需要的变量。

它的定义是:

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

我已经将 rects 和 count 定义为:

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

这似乎有效。调试器没有提供任何方便的东西来查看指针中的内容，所以这没有帮助。

在调用 getRectsBeingDrawn 之后，

rect 应该指向一个NSRect 数组，但它似乎没有返回任何内容。另外，如何获取 rects 和 count 指向的数组和 int？

我正在尝试从 Apple 示例“TableViewPlayground”中获取一段代码以快速工作。

- (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

我已经设法弄清楚了...我没有为 rects 和 count 正确分配内存

我得到的是:

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

最终解决问题的是:

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

希望这对其他人有帮助:)

edit 如果有人感兴趣，下面是上面的 swift 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

根据进一步的评论，这里用一种不太冗长的方法实现了同样的效果(感谢下面的 Paul Patterson):

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