Declare a block method parameter without using a typedef

问题

Is it possible to specify a method block parameter in Objective-C without using a typedef? It must be, like function pointers, but I can't hit on the winning syntax without using an intermediate typedef:

typedef BOOL (^PredicateBlock_t)(int);
- (void) myMethodTakingPredicate:(PredicateBlock_t)predicate

only the above compiles, all these fail:

-  (void) myMethodTakingPredicate:( BOOL(^block)(int) ) predicate
-  (void) myMethodTakingPredicate:BOOL (^predicate)(int)

and I can't remember what other combinations I've tried.

回答1:

- ( void )myMethodTakingPredicate: ( BOOL ( ^ )( int ) )predicate

回答2:

This is how it goes, for example...

[self smartBlocks:@"Pen" youSmart:^(NSString *response) {
        NSLog(@"Response:%@", response);
    }];


- (void)smartBlocks:(NSString *)yo youSmart:(void (^) (NSString *response))handler {
    if ([yo compare:@"Pen"] == NSOrderedSame) {
        handler(@"Ink");
    }
    if ([yo compare:@"Pencil"] == NSOrderedSame) {
        handler(@"led");
    }
}

回答3:

http://fuckingblocksyntax.com

As a method parameter:

- (void)someMethodThatTakesABlock:(returnType (^)(parameterTypes))blockName;

回答4:

Another example (this issue benefits from multiple):

@implementation CallbackAsyncClass {
void (^_loginCallback) (NSDictionary *response);
}
// …


- (void)loginWithCallback:(void (^) (NSDictionary *response))handler {
    // Do something async / call URL
    _loginCallback = Block_copy(handler);
    // response will come to the following method (how is left to the reader) …
}

- (void)parseLoginResponse {
    // Receive and parse response, then make callback

   _loginCallback(response);
   Block_release(_loginCallback);
   _loginCallback = nil;
}


// this is how we make the call:
[instanceOfCallbackAsyncClass loginWithCallback:^(NSDictionary *response) {
   // respond to result
}];

回答5:

Even more clear !

[self sumOfX:5 withY:6 willGiveYou:^(NSInteger sum) {
    NSLog(@"Sum would be %d", sum);
}];

- (void) sumOfX:(NSInteger)x withY:(NSInteger)y willGiveYou:(void (^) (NSInteger sum)) handler {
    handler((x + y));
}

来源：https://stackoverflow.com/questions/5486976/declare-a-block-method-parameter-without-using-a-typedef

标签

objective-c

parameters

objective-c-blocks