blocks|key|1961856|text|块的类型因其参数和返回类型而异。在一般情况下，声明块类型的方式与声明函数指针类型的方式相同，但用%5E替换*。将块传递给方法的一种方法如下：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1961857|-+(void)iterateWidgets:(void+(%5E)(id,+int))iteratorBlock;|code-block|syntax|javascript|1961858|但正如你所见，这是混乱的。您可以改为使用typedef来使块类型更清晰：|1961859|typedef+void+(%5E+IteratorBlock)(id,+int);|1961860|然后将该块传递给如下所示的方法：|1961861|-+(void)iterateWidgets:(IteratorBlock)iteratorBlock;|1961862|entityMap^0|1C|1|1F|1|0|0|K|7|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|14|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|T|$]]

The type of a block varies depending on its arguments and its return type. In the general case, block types are declared the same way function pointer types are, but replacing the <code>*</code> with a <code>^</code>. One way to pass a block to a method is as follows:

<pre><code>- (void)iterateWidgets:(void (^)(id, int))iteratorBlock;
</code></pre>

But as you can see, that's messy. You can instead use a <code>typedef</code> to make block types cleaner:

<pre><code>typedef void (^ IteratorBlock)(id, int);
</code></pre>

And then pass that block to a method like so:

<pre><code>- (void)iterateWidgets:(IteratorBlock)iteratorBlock;
</code></pre>

blocks|key|1748602|text|这可能会有所帮助：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1748603|-+(void)someFunc:(void(%5E)(void))someBlock;|code-block|syntax|javascript|1748604|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This might be helpful:

<pre><code>- (void)someFunc:(void(^)(void))someBlock;
</code></pre>

blocks|key|1748880|text|您可以这样做，将block作为block参数传递：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1748881|//creating+a+block+named+"completion"+that+will+take+no+arguments+and+will+return+void
void(%5Ecompletion)()+=+%5E()+{
++++NSLog(@"bbb");
};

//creating+a+block+namd+"block"+that+will+take+a+block+as+argument+and+will+return+void
void(%5Eblock)(void(%5Ecompletion)())+=+%5E(void(%5Ecompletion)())+{
++++NSLog(@"aaa");
++++completion();
};

//invoking+block+"block"+with+block+"completion"+as+argument
block(completion);|code-block|syntax|javascript|1748882|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can do like this, passing block as a block parameter:

<pre><code>//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);
</code></pre>

blocks|key|1962447|text|使用下面示例中的с函数传递块的另一种方法。我已经创建了在后台和主队列上执行任何操作的函数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1962448|blocks.h+s.h文件|1962449|void+performInBackground(void(%5Eblock)(void));
void+performOnMainQueue(void(%5Eblock)(void));|code-block|syntax|javascript|1962450|blocks.m+s.m文件|1962451|#import+"blocks.h"

void+performInBackground(void(%5Eblock)(void))+{
++++if+(nil+==+block)+{
++++++++return;
++++}

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

void+performOnMainQueue(void(%5Eblock)(void))+{
++++if+(nil+==+block)+{
++++++++return;
++++}

++++dispatch_async(dispatch_get_main_queue(),+block);
}|1962452|然后在必要时导入blocks.h+s.h并调用它：|1962453|-+(void)loadInBackground+{

++++performInBackground(%5E{

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

++++++++performOnMainQueue(%5E{
++++++++++++//completion+hadler+code+on+main+queue
++++++++});
++++});
}|1962454|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

One more way to pass block using с functions in example below. 
I`ve created functions to perform anything in background and on main queue.

blocks.h file

<pre><code>void performInBackground(void(^block)(void));
void performOnMainQueue(void(^block)(void));
</code></pre>

blocks.m file

<pre><code>#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);
}
</code></pre>

Than import blocks.h when necessary and invoke it:

<pre><code>- (void)loadInBackground {

 performInBackground(^{

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

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

blocks|key|1748825|text|你也可以将block设置为一个简单的属性，如果它适合你的话：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1748826|@property+(nonatomic,+copy)+void+(%5EdidFinishEditingHandler)(float+rating,+NSString+*reviewString);|code-block|syntax|javascript|1748827|确保block属性为"copy"！|1748828|当然，您也可以使用typedef：|1748829|typedef+void+(%5ESimpleBlock)(id);

@property+(nonatomic,+copy)+SimpleBlock+someActionHandler;|1748830|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

You also can set block as a simple property if it's applicable for you:

<pre><code>@property (nonatomic, copy) void (^didFinishEditingHandler)(float rating, NSString *reviewString);
</code></pre>

make sure that block property is "copy"!

and of course you can also use typedef:

<pre><code>typedef void (^SimpleBlock)(id);

@property (nonatomic, copy) SimpleBlock someActionHandler;
</code></pre>

blocks|key|1748686|text|此外，还可以使用常用的c函数语法在中调用或调用块。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1748687|-(void)iterateWidgets:(IteratorBlock)iteratorBlock{

++++iteratorBlock(someId,+someInt);
}|code-block|syntax|javascript|1748688|有关块的更多信息，请单击此处|1748689|http://developer.apple.com/library/ios/#documentation/cocoa/Conceptual/Blocks/Articles/bxGettingStarted.html#//apple_ref/doc/uid/TP40007502-CH7-SW1|offset|length|1748690|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|0|43|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|V|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|W|8|@]|9|@$K|X|L|Y|1|Z]]|A|$]]|$1|M|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|J]]]]

Also you invoke or call a block in using usual c function syntax

<pre><code>-(void)iterateWidgets:(IteratorBlock)iteratorBlock{

 iteratorBlock(someId, someInt);
}
</code></pre>

More info on blocks here

<a href="http://developer.apple.com/library/ios/#documentation/cocoa/Conceptual/Blocks/Articles/bxGettingStarted.html#//apple_ref/doc/uid/TP40007502-CH7-SW1" rel="nofollow noreferrer">http://developer.apple.com/library/ios/#documentation/cocoa/Conceptual/Blocks/Articles/bxGettingStarted.html#//apple_ref/doc/uid/TP40007502-CH7-SW1</a>

blocks|key|1749356|text|我总是倾向于忘记块语法。当我需要声明一个块时，我总是会想到这一点。我希望它能帮助某些人:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1749357|http://fuckingblocksyntax.com|offset|length|1749358|entityMap|0|LINK|mutability|MUTABLE|url|http://fuckingblocksyntax.com/^0|0|0|T|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

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 :)

<a href="http://fuckingblocksyntax.com" rel="nofollow">http://fuckingblocksyntax.com</a>

blocks|key|1749327|text|尽管在这个帖子上给出了答案，但我真的很难写出一个函数，它将一个Block作为一个函数-并带有一个参数。最终，这是我想出的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1749328|我想编写一个泛型函数loadJSONthread，它将获取JSON+Web+Service的URL，在后台线程上从该URL加载一些JSON数据，然后将结果的NSArray*返回给调用函数。|offset|length|style|CODE|1749329|基本上，我希望将所有后台线程的复杂性隐藏在一个通用的可重用函数中。|1749330|下面是我调用这个函数的方式：|1749331|NSString*+WebServiceURL+=+@"http://www.inorthwind.com/Service1.svc/getAllCustomers";

[JSONHelper+loadJSONthread:WebServiceURL+onLoadedData:%5E(NSArray+*results)+{

++++//++Finished+loading+the+JSON+data
++++NSLog(@"Loaded+%25lu+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)
++++}

}+];|code-block|syntax|javascript|1749332|这就是我努力的地方:如何声明它，以及如何让它在数据加载后调用...and函数，并将加载的记录的NSArray*传递给Block：|1749333|%2B(void)loadJSONthread:(NSString*)urlString+onLoadedData:(void+(%5E)(NSArray*))onLoadedData
{
++++__block+NSArray*+results+=+nil;

++++dispatch_queue_t+queue+=+dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,+0);
++++dispatch_async(queue,+%5E{

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

++++++++dispatch_async(dispatch_get_main_queue(),+%5E{

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

++++++++});
++++});
}|1749334|这个块问题涉及如何调用函数，将块作为参数传递，因此我简化了上面的代码，没有包含loadJSONDataFromURL函数。|1749335|但是，如果您感兴趣，可以在这个博客上找到这个JSON加载函数的副本：http://mikesknowledgebase.azurewebsites.net/pages/Services/WebServices-Page6.htm|1749336|希望这对其他XCode开发人员有所帮助！(如果是这样，不要忘了投票支持这个问题和我的答案!)|1749337|entityMap|0|LINK|mutability|MUTABLE|url|http://mikesknowledgebase.azurewebsites.net/pages/Services/WebServices-Page6.htm^0|0|A|E|0|0|0|0|1M|5|0|0|13|J|0|Y|28|0|0|0^^$0|@$1|2|3|4|5|6|7|18|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|19|8|@$D|1A|E|1B|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|1C|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|1D|8|@]|9|@]|A|$]]|$1|L|3|M|5|N|7|1E|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1F|8|@$D|1G|E|1H|F|G]]|9|@]|A|$]]|$1|S|3|T|5|N|7|1I|8|@]|9|@]|A|$O|P]]|$1|U|3|V|5|6|7|1J|8|@$D|1K|E|1L|F|G]]|9|@]|A|$]]|$1|W|3|X|5|6|7|1M|8|@]|9|@$D|1N|E|1O|1|1P]]|A|$]]|$1|Y|3|Z|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1R|8|@]|9|@]|A|$]]]|11|$12|$5|13|14|15|A|$16|17]]]]

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, <code>loadJSONthread</code>, 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:

<pre><code>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)
 }

} ];
</code></pre>

...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 <code>Block</code> an NSArray* of records loaded:

<pre><code>+(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);

 });
 });
}
</code></pre>

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 <code>loadJSONDataFromURL</code> function. 

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

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

blocks|key|1962790|text|完整的模板如下所示|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1962791|-+(void)+main+{
++++//Call
++++[self+someMethodWithSuccessBlock:%5E{[self+successMethod];}
++++++++++++++++++++withFailureBlock:%5E(NSError+*+error)+{[self+failureMethod:error];}];
}

//Definition
-+(void)+someMethodWithSuccessBlock:(void+(%5E)+(void))successBlock
+++++++++++++++++++withFailureBlock:(void+(%5E)+(NSError*))failureBlock+{
++++
++++//Execute+a+block
++++successBlock();
++++failureBlock([[NSError+alloc]init]);
}

-+(void)+successMethod+{
}

-+(void)+failureMethod:(NSError*)+error+{
}|code-block|syntax|javascript|1962792|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The full template looks like
<pre><code>- (void) main {
 //Call
 [self someMethodWithSuccessBlock:^{[self successMethod];}
 withFailureBlock:^(NSError * error) {[self failureMethod:error];}];
}

//Definition
- (void) someMethodWithSuccessBlock:(void (^) (void))successBlock
 withFailureBlock:(void (^) (NSError*))failureBlock {
 
 //Execute a block
 successBlock();
 failureBlock([[NSError alloc]init]);
}

- (void) successMethod {
}

- (void) failureMethod:(NSError*) error {
}
</code></pre>

How can I pass a <code>Block</code> to a <code>Function</code>/<code>Method</code>?

I tried <code>- (void)someFunc:(__Block)someBlock</code> with no avail.

ie. What is the type for a <code>Block</code>?

Objective-C pass block as parameter

如何将Block传递给Function/Method我尝试了- (void)someFunc:(__Block)someBlock，但没有效果。即。Block的类型是什么

问Objective-C传递块作为参数
EN

回答 9

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