嵌套objective-c块时的语法/格式

Question

我是嵌套块,它看起来像UGGGGLY.有没有办法写这个不那么难看？主要是寻找语法建议,而不是结构,但我也会接受.

我的块工厂方法,

-(NSImage *(^)(CGFloat size, BOOL preview))resizeBlock {

return (NSImage *(^)(CGFloat size, BOOL preview))[[^(CGFloat size, BOOL preview){
        // image-resizing code
        return [[[NSImage alloc] init] autorelease];
    } copy] autorelease];

}

从许多类似于此的函数调用

-(void)queueResize:(CGFloat)targetSize toView:(NSImageView *)targetView {
    NSImage*(^sizeBlock)(CGFloat,BOOL) = [self resizeBlock];
    NSBlockOperation *bo = [NSBlockOperation blockOperationWithBlock:^(void) {
        NSImage *previewImage = (NSImage*)sizeBlock(targetSize,YES);
        targetView.image = previewImage;
    }];
    [queue addOperation:bo];
}

queue是一个NSOperationQueue对象.没有所有(丑陋的丑陋)演员,它将无法编译.Amidoinitrite？

编辑:根据Dave DeLong的回答,和http://www.cimgf.com/2008/02/16/cocoa-tutorial-nsoperation-and-nsoperationqueue/,我改变了行

targetView.image = previewImage;

成为,

[targetView performSelectorOnMainThread:@selector(setImage:) withObject:previewImage waitUntilDone:YES];

Answer 1

用途typedef:

typedef NSImage *(^KWResizerBlock)(CGFloat size, BOOL preview);

这使您的代码成为:

- (KWResizerBlock) resizeBlock {
  KWResizerBlock block = ^(CGFloat size, BOOL preview){
    // image-resizing code
    return [[[NSImage alloc] init] autorelease];
  };
  return [[block copy] autorelease];
}

-(void)queueResize:(CGFloat)targetSize toView:(NSImageView *)targetView {
  KWResizerBlock sizeBlock = [self resizeBlock];
  NSBlockOperation *bo = [NSBlockOperation blockOperationWithBlock:^{
    NSImage *previewImage = sizeBlock(targetSize, YES);
    //do something with previewImage
  }];
  [queue addOperation:bo];
}

提醒一句:

您NSBlockOperation将在不是主线程的线程上执行,因此从该上下文中操作任何UI元素是不安全的.如果你需要把它previewImage放到UI上,那么你应该dispatch_async()回到主线程(或者功能相当的东西).

它现在可能有效,但强烈反对,可能会导致未定义的行为.