完成塊的不予執行

Question

這裏是塊電話：

[VacationHelper openVacationWithName:vacationName 
       usingBlock:^(UIManagedDocument *vacationDocument) { 
    NSLog(@"vacationDocument.description:%@", vacationDocument.description); 
}]; 

在接收方法的.H：

typedef void (^completion_block_t)(UIManagedDocument *vacationDocument); 

而在.M：

+ (void)openVacationWithName:(NSString *)vacationName 
        usingBlock:(completion_block_t)completionBlock; 
{ 
    NSLog(@"Opening Vacation Document"); 

    // Get documents directory and path. 
    NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]; 
    url  = [url URLByAppendingPathComponent:vacationName]; 

    // Create the document and open if a match exists on file. 
    UIManagedDocument *vacationDocument = [[UIManagedDocument alloc] initWithFileURL:url]; 
    if ([[NSFileManager defaultManager] fileExistsAtPath:[url path]]) { 
     NSLog(@"vacationDocument.documentState:%i", vacationDocument.documentState); 
     [vacationDocument openWithCompletionHandler:^(BOOL success) { 
      if (success) NSLog(@"Document was opened."); 
      else NSLog (@"Couldn't open document at %@", url); 
     }]; 
    } else { 

     // No match exists, so save the document to file. 
     [vacationDocument saveToURL:url forSaveOperation:UIDocumentSaveForCreating 
        completionHandler:^(BOOL success) { 
         if (success) NSLog(@"Document was created."); 
         else NSLog(@"Couldn't create document at %@", url); 
        }]; 
    } 
    NSLog(@"Exiting helper."); 
} 

我問題是爲什麼執行沒有達到在openVacationWithName:調用中傳遞的塊？我從來沒有看到寫的NSLog。

我懷疑openVacationWithName:沒有完成，但NSLog的「退出幫助」。打印。任何指導讚賞。僅供參考iTunes U/Stanford CS193P作業＃6。

Answer 1

你不叫completionBlock裏面openVacationWithName:usingBlock:。也許你想在方法結束做到這一點：

... 
    if (completionBlock) { 
    completionBlock(vacationDocument); 
    } 

    NSLog(@"Exiting helper."); 
} 

（在這種情況下，也許會更有意義只返回UIManagedDocument）

或者，也許裏面那些completionHandler S IN方法openWithCompletionHandler:和saveToUrl:forSaveOperation:completionHandler:：

... ^(BOOL success) { 
    if (success) { 
    NSLog(@"Document was created."); 
    } 
    else { 
    NSLog(@"Couldn't create document at %@", url); 
    } 

    if (completionBlock) { 
    completionBlock(vacationDocument); 
    } 
} ...