如何调用接受块字典作为来自 Swift 的参数的 objective-c 函数？

Question

我的 objective c 文件中有一个函数（比方说 class MyBlockExecutor）：

+ (void) runBlockFromDictionary: (NSDictionary*) blocksDict andKey: (NSString*) key
{
    if ( [blocksDict objectForKey: key] != nil )
    {
         ((MyBlock)[blocksDict objectForKey: key])();
    }
}

现在，我想从 Swift 调用这个函数。这是我的 swift 电话：

MyBlockExecutor.runBlock(from: [
        "key1":{ ()->Void in
                    print("block for key1 called")
               }
        ], andKey: "key1")

这会使我的应用程序崩溃。我在这一行收到 EXC_BAD_ACCESS 错误：

((MyBlock)[blocksDict objectForKey: key])();

不过，从 Objective-C 调用相同的函数工作得很好。另外，我将 MyBlock 定义为：

typedef void (^MyBlock)(); //defined in MyBlockExecutor.h file

我该如何解决这个问题？

编辑：我对 objective c 函数的变化持开放态度，我只是需要以某种方式将闭包集合从 swift 传递到我的 objective c 函数和运行块。

Answer 1

尝试分段分解代码并检查错误来源..虽然它几乎与您所做的相同，但我们只是将代码分解为多行以便于调试

//1. create the block instance separately
let myBlockForKey1:MyBlock = { () in
    print("block for key1 called")
}
//2. create dic of blocks as
let dicOfBlocks:[String:MyBlock] = ["key1":myBlockForKey1]
//3. call your function
MyBlockExecutor.runBlock(from: dicOfBlocks, andKey: "key1")

Answer 2

您可以使用与 Swift blocks not working 类似的方法：用 @convention(block) 注释块使用 Objective-C 块调用约定，并（明确地）强制转换在将其放入字典之前将其设置为 AnyObject:

let myBlock: @convention(block) () -> Void = {
    print("block for key1 called")
}

let dict = ["key1": myBlock as AnyObject]

MyBlockExecutor.runBlock(from: dict, andKey: "key1")

这在我的测试中按预期工作。

也和奎因的《爱斯基摩人！建议在 the Apple developer forum 作为一种方法将闭包（在 Swift 中定义）作为 Objective-C 兼容传递通过指针对象，只是我替换了 unsafeBitCast 通过更简单的 as AnyObject.

您也可以内联编写所有内容：

MyBlockExecutor.runBlock(from: ["key1": {
        print("block for key1 called")
    } as @convention(block) () -> Void as AnyObject
    ], andKey: "key1")

或定义辅助函数：

func objcBlock(from block: @convention(block) () -> Void) -> AnyObject {
    return block as AnyObject
}

MyBlockExecutor.runBlock(from: ["key1": objcBlock {
        print("block for key1 called")
    }], andKey: "key1")

如何调用接受块字典作为来自 Swift 的参数的 objective-c 函数？

How to call an objective-c function which accepts Dictionary of blocks as argument from Swift?

closures

objective-c

objective-c-blocks

swift