ios - 从 Swift 调用存储在 NSDictionary 中的 Objective-C block

Question

预期结果:我创建了一个 block ，将其存储在 NSDictionary 中，将字典传递给 Swift 类，从字典中检索 block ，然后调用 block 。

实际结果:从字典中检索 block 会导致 EXC_BAD_INSTRUCTION。

示例代码 Obj-C View Controller :

- (void)viewDidLoad {
    [super viewDidLoad];

    void (^completionHandler)() = ^() {
        [self printBlahBlah];
    };

    NSDictionary *dict = @{@"blah":completionHandler};
    Nav *nav = [Nav new];
    [nav done:dict];
}

-(void)printBlahBlah { NSLog(@"BlahBlah"); }

Nav Swift 类的示例代码:

@objc public class Nav : NSObject {

    @objc public func done(dict: NSDictionary){
        let block = dict["blah"] as! ()->Void //EXC_BAD_INSTRUCTION
        block()
    }
}

Answer 1

所以这是可行的:

@objc public class Nav : NSObject {

    typealias MyFunBlock = @convention(block) () -> Void;

    @objc public func done(dict: NSDictionary){
        let block = unsafeBitCast(dict["blah"], BoolBlock.self) as BoolBlock?
        block?()
    }
}

但是 unsafeBitCast 的文档说:

/// Returns the bits of `x`, interpreted as having type `U`.
///
/// - Warning: Breaks the guarantees of Swift's type system; use
///   with extreme care.  There's almost always a better way to do
///   anything.
///
@warn_unused_result
public func unsafeBitCast<T, U>(x: T, _: U.Type) -> U

我觉得我不想用这个。

功劳真的归功于这个人:https://stackoverflow.com/a/28376909/1366911