매개 변수로서 Objective-C 패스 블록

매개 변수로서 Objective-C 패스 블록

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어떻게 전달할 수 BlockA를 Function/ Method?

나는 - (void)someFunc:(__Block)someBlock아무 소용없이 노력했다 .

즉. 이란 무엇입니까 타입 A의는 Block?

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블록의 유형은 인수 및 반환 유형에 따라 다릅니다. 일반적인 경우, 블록 유형의 함수 포인터 유형은 동일한 방식으로 선언되어 있지만 교체 *로모그래퍼 ^. 메소드에 블록을 전달하는 한 가지 방법은 다음과 같습니다.

- (void)iterateWidgets:(void (^)(id, int))iteratorBlock;

그러나 보시다시피 지저분합니다. 대신 a typedef를 사용하여 블록 유형을 더 깨끗하게 만들 수 있습니다 .

typedef void (^ IteratorBlock)(id, int);

그런 다음 해당 블록을 다음과 같은 방법으로 전달하십시오.

- (void)iterateWidgets:(IteratorBlock)iteratorBlock;

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이 질문에 대한 가장 쉬운 설명은 다음 템플릿을 따르는 것입니다.

1. 메소드 매개 변수로 차단

주형

- (void)aMethodWithBlock:(returnType (^)(parameters))blockName {
        // your code
}

예

-(void) saveWithCompletionBlock: (void (^)(NSArray *elements, NSError *error))completionBlock{
        // your code
}

다른 경우 사용 :

2. 속성으로 차단

주형

@property (nonatomic, copy) returnType (^blockName)(parameters);

예

@property (nonatomic,copy)void (^completionBlock)(NSArray *array, NSError *error);

3. 메소드 인수로 차단

주형

[anObject aMethodWithBlock: ^returnType (parameters) {
    // your code
}];

예

[self saveWithCompletionBlock:^(NSArray *array, NSError *error) {
    // your code
}];

4. 지역 변수로 차단

주형

returnType (^blockName)(parameters) = ^returnType(parameters) {
    // your code
};

예

void (^completionBlock) (NSArray *array, NSError *error) = ^void(NSArray *array, NSError *error){
    // your code
};

5. typedef로 차단

주형

typedef returnType (^typeName)(parameters);

typeName blockName = ^(parameters) {
    // your code
}

예

typedef void(^completionBlock)(NSArray *array, NSError *error);

completionBlock didComplete = ^(NSArray *array, NSError *error){
    // your code
};

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도움이 될 수 있습니다.

- (void)someFunc:(void(^)(void))someBlock;

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다음과 같이 블록을 블록 매개 변수로 전달하면됩니다 :

//creating a block named "completion" that will take no arguments and will return void
void(^completion)() = ^() {
    NSLog(@"bbb");
};

//creating a block namd "block" that will take a block as argument and will return void
void(^block)(void(^completion)()) = ^(void(^completion)()) {
    NSLog(@"aaa");
    completion();
};

//invoking block "block" with block "completion" as argument
block(completion);

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아래 예에서 с 함수를 사용하여 블록을 전달하는 또 다른 방법입니다. 백그라운드와 메인 큐에서 무엇이든 수행하는 기능을 만들었습니다.

blocks.h 파일

void performInBackground(void(^block)(void));
void performOnMainQueue(void(^block)(void));

blocks.m 파일

#import "blocks.h"

void performInBackground(void(^block)(void)) {
    if (nil == block) {
        return;
    }

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), block);
}

void performOnMainQueue(void(^block)(void)) {
    if (nil == block) {
        return;
    }

    dispatch_async(dispatch_get_main_queue(), block);
}

필요한 경우 import blocks.h보다 다음을 호출하십시오.

- (void)loadInBackground {

    performInBackground(^{

        NSLog(@"Loading something in background");
        //loading code

        performOnMainQueue(^{
            //completion hadler code on main queue
        });
    });
}

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해당되는 경우 블록을 간단한 속성으로 설정할 수도 있습니다.

@property (nonatomic, copy) void (^didFinishEditingHandler)(float rating, NSString *reviewString);

블록 속성이 "복사"인지 확인하십시오!

물론 typedef를 사용할 수도 있습니다.

typedef void (^SimpleBlock)(id);

@property (nonatomic, copy) SimpleBlock someActionHandler;

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또한 일반적인 c 함수 구문을 사용하여 블록을 호출하거나 호출합니다.

-(void)iterateWidgets:(IteratorBlock)iteratorBlock{

    iteratorBlock(someId, someInt);
}

여기 블록에 대한 자세한 정보

http://developer.apple.com/library/ios/#documentation/cocoa/Conceptual/Blocks/Articles/bxGettingStarted.html#//apple_ref/doc/uid/TP40007502-CH7-SW1

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I always tend to forget about blocks syntax. This always comes to my mind when I need to declare a block. I hope it helps someone :)

http://fuckingblocksyntax.com

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Despite the answers given on this thread, I really struggled to write a function which would take a Block as a function - and with a parameter. Eventually, here's the solution I came up with.

I wanted to write a generic function, loadJSONthread, which would take the URL of a JSON Web Service, load some JSON data from this URL on a background thread, then return an NSArray* of results back to the calling function.

Basically, I wanted to keep all the background-thread complexity hidden away in a generic reuseable function.

Here's how I would call this function:

NSString* WebServiceURL = @"http://www.inorthwind.com/Service1.svc/getAllCustomers";

[JSONHelper loadJSONthread:WebServiceURL onLoadedData:^(NSArray *results) {

    //  Finished loading the JSON data
    NSLog(@"Loaded %lu rows.", (unsigned long)results.count);

    //  Iterate through our array of Company records, and create/update the records in our SQLite database
    for (NSDictionary *oneCompany in results)
    {
        //  Do something with this Company record (eg store it in our SQLite database)
    }

} ];

...and this is the bit I struggled with: how to declare it, and how to get it to call the Block function once the data was loaded, and pass the Block an NSArray* of records loaded:

+(void)loadJSONthread:(NSString*)urlString onLoadedData:(void (^)(NSArray*))onLoadedData
{
    __block NSArray* results = nil;

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^{

        // Call an external function to load the JSON data 
        NSDictionary * dictionary = [JSONHelper loadJSONDataFromURL:urlString];
        results = [dictionary objectForKey:@"Results"];

        dispatch_async(dispatch_get_main_queue(), ^{

            // This code gets run on the main thread when the JSON has loaded
            onLoadedData(results);

        });
    });
}

This StackOverflow question concerns how to call functions, passing a Block as a parameter, so I've simplified the code above, and not included the loadJSONDataFromURL function.

But, if you are interested, you can find a copy of this JSON loading function on this blog: http://mikesknowledgebase.azurewebsites.net/pages/Services/WebServices-Page6.htm

Hope this helps some other XCode developers ! (Don't forget to vote up this question and my answer, if it does !)

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I wrote a completionBlock for a class which will return the values of dice after they have been shaken:

1. Define typedef with returnType (.h above @interface declaration)

   typedef void (^CompleteDiceRolling)(NSInteger diceValue);
   

2. Define a @property for the block (.h)

   @property (copy, nonatomic) CompleteDiceRolling completeDiceRolling;
   

3. Define a method with finishBlock (.h)

   - (void)getDiceValueAfterSpin:(void (^)(NSInteger diceValue))finishBlock;
   

4. Insert previous defined method in .m file and commit finishBlock to @property defined before

   - (void)getDiceValueAfterSpin:(void (^)(NSInteger diceValue))finishBlock{
       self.completeDiceRolling = finishBlock;
   }
   

5. To trigger completionBlock pass predefined variableType to it (Don't forget to check whether the completionBlock exists)

   if( self.completeDiceRolling ){
       self.completeDiceRolling(self.dieValue);
   }
   

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The full template looks like

- (void) main {
    [self someMethodWithSuccessBlock:^{[self successMethod];}
                    withFailureBlock:^(NSError * error) {[self failureMethod:error];}];
}

- (void) someMethodWithSuccessBlock:(void (^) (void))successBlock
                   withFailureBlock:(void (^) (NSError*))failureBlock {

    //Execute a block
    successBlock();
//    failureBlock([[NSError alloc]init]);

}

- (void) successMethod {

}

- (void) failureMethod:(NSError*) error {

}

참고URL : https://stackoverflow.com/questions/7936570/objective-c-pass-block-as-parameter