objective-c - 您如何将此 enumerateDraggingItemsWithOptions 方法调用转换为 Swift？

Question

名为 CocoaDragAndDrop 的示例应用程序使用名为 enumerateDraggingItemsWithOptions 的方法。这是在 Obj-C 中:

    [sender enumerateDraggingItemsWithOptions:NSDraggingItemEnumerationConcurrent 
        forView:self
        classes:[NSArray arrayWithObject:[NSPasteboardItem class]] 
        searchOptions:nil 
        usingBlock:^(NSDraggingItem *draggingItem, NSInteger idx, BOOL *stop) {


            if ( ![[[draggingItem item] types] containsObject:kPrivateDragUTI] ) {

                *stop = YES;

            } else {

                [draggingItem setDraggingFrame:self.bounds contents:[[[draggingItem imageComponents] objectAtIndex:0] contents]];
            }
        }];

你会如何在 swift 中编写这段代码？

我试过这样的:

sender.enumerateDraggingItemsWithOptions(
    enumOptions: NSDraggingItemEnumerationOptions.Concurrent,
    forView: self,
    classes: [NSPasteboardItem.self],
    searchOptions: NSPasteboardURLReadingFileURLsOnlyKey,
    usingBlock: { (draggingItem: NSDraggingItem, idx: Int, stop: UnsafeMutablePointer<ObjCBool>) -> Void in

        // ...

    }
)

我收到以下错误:

Cannot convert the expression's type '(enumOptions: NSDraggingItemEnumerationOptions, forView: DragDropImageView, classes: $T5, searchOptions: NSString!, usingBlock: (NSDraggingItem, Int, UnsafeMutablePointer<ObjCBool>) -> Void)' to type 'NSPasteboardItem.Type'

Answer 1

Swift 中的方法签名是

func enumerateDraggingItemsWithOptions(enumOpts: NSDraggingItemEnumerationOptions, 
  forView view: NSView, classes 
  classArray: [AnyObject], 
  searchOptions: [NSObject : AnyObject], 
  usingBlock block: (NSDraggingItem!, Int, UnsafeMutablePointer<ObjCBool>) -> Void)

• 我们可以在回调中省略参数类型，因为它们是从声明中获取的，使代码更干净
• 回调是最后一个参数所以我们可以使用trailing closure句法

调用方法

sender.enumerateDraggingItemsWithOptions(
  .Concurrent,
  forView: self,
  classes: [NSPasteboardItem.self],
  searchOptions: [NSPasteboardURLReadingFileURLsOnlyKey:self]) 
    {(draggingItem, idx, stop)  in
    // Code here
  }