Question

以下代码取自FastImageCache git存储库。我怎么能在Swift中写这个？

FICEntityImageDrawingBlock drawingBlock = ^(CGContextRef context, CGSize contextSize) 
{
     CGRect contextBounds = CGRectZero;
     contextBounds.size = contextSize;
     CGContextClearRect(context, contextBounds);

     ....

     UIGraphicsPopContext();
};

Answer 1

试试这个：

let drawingBlock: FICEntityImageDrawingBlock = { context, contextSize in
    let contextBounds = CGRectZero
    contextBounds.size = contextSize
    CGContextClearRect(context, contextBounds)

    ...

    UIGraphicsPopContext()
}

Answer 2

这就是它的外观，主要变化是第一行，您使用(parameters) in。

let drawingBlock: FICEntityImageDrawingBlock = { (context: CGContextRef, size: CGSize) in
    let bounds = CGRect(origin: .zero, size: size)
    CGContextClearRect(context, bounds);
    //...
    UIGraphicsPopContext();
}

Answer 3

我已将目标C块代码转换为Swift代码...

// Object-C FICEntityImageDrawingBlock definition 
// void (^FICEntityImageDrawingBlock)(CGContextRef context, CGSize contextSize);
// Swift code
let drawingBlock : FICEntityImageDrawingBlock = {( context, contextSize) in
            var contextBounds : CGRect = CGRectZero;
            contextBounds.size = contextSize;
            CGContextClearRect(context, contextBounds);
            UIGraphicsPopContext();
        }

您还可以非常轻松地将任何Objective-C块代码转换为swift代码。看看另一个例子 -

 // Objecttive C Block
   void (^completionBlock)(NSData *, NSError *) = ^(NSData *data, NSError *error) {
            // ...
        }

 // Swift Block
    let completionBlock: (NSData, NSError) -> Void = { (data, error) in
            // ...
        }

有关详细信息，请参阅apple documentation

如何在Swift中写这个？

3 个答案: