UITableView：cell.textLabel.text錯誤：[__NSArrayI isEqualToString：]

Question

我正在下載一個NSManagedObject。將NSString分配給該對象的valueForKey @「username」。接下來，我將該字符串分配給UITableView中的cell.textLabel.text，並且出現異常。

以下是這就是代碼拋出異常：

-(NSString *)fetchUserName 
{ 
    if ([fetchedUserNameObject objectAtIndex:0]!= NULL) 
    { 
     recipientUser = (User*)(fetchedUserNameObject); 
     NSString *userName = (NSString*)[recipientUser valueForKey:@"username"];    
     return userName; 
    } 
} 

.....

 NSString *recipientUserName = [self fetchUserName] 

......

- (IBAction)reviewButtonPressed:(UIBarButtonItem *)sender 
{ 
    NSLog(@"Recipient UserName from Review Button %@", recipientUserName); 

    PDReviewVC *modalVC = [self.storyboard instantiateViewControllerWithIdentifier:@"pdReview"]; 
    UINavigationController *navBar=[[UINavigationController alloc]initWithRootViewController:modalVC]; 

    modalVC.recipientUserName= self.recipientUserName; 
    [self presentViewController:navBar animated:YES completion:NULL]; 

} 

登錄

2013-08-30 11:51:49.393 Time[1188:c07] Recipient UserName from Review Button (
     iphone3gs 
    ) 

現在PDReviewVC：

.H

@property (nonatomic, retain) NSString * recipientUserName; 

.M

@synthesize recipientUserName; 

... //的cellForRowAtIndexPath

if (indexPath.section == 0) 
{ 
    cell.textLabel.text = recipientUserName; 
} 

我收到以下錯誤上cell.textLabel.text = recipientUserName ;:

2013-08-30 11:51:54.679 Time[1188:c07] -[__NSArrayI isEqualToString:]: unrecognized selector sent to instance 0xb889390 
2013-08-30 11:53:53.303 Time[1188:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayI isEqualToString:]: unrecognized selector sent to instance 0xb889390' 
*** First throw call stack: 

UPDATE

的NSLog以下代碼：

if ([fetchedUserNameObject objectAtIndex:0]!= NULL) 
{ 
    recipientUser = (User*)(fetchedUserNameObject); 
    NSLog(@"User %@", recipientUser); 
    NSString *userName = (NSString*)[recipientUser valueForKey:@"username"]; 
    NSLog (@"userName from fetchUserName: %@", userName); 
    NSLog(@"%@", userName); 

    return userName; 

} 
else return NULL; 

的NSLog：

2013-08-30 12:36:29.495 Time[1341:c07] User (
    "<User: 0xa55cd60> (entity: User; id: 0xa5a0ae0 <x-coredata://3B273CFB-1CAA-4FA0-95DC-BA9420219380-1341-000007F42366B21A/User/piphone3gs> ; data: <fault>)" 
) 
2013-08-30 12:36:29.496 Time[1341:c07] userName from fetchUserName: (
    iphone3gs 
) 
2013-08-30 12:36:29.496 Time[1341:c07] (
    iphone3gs 
) 

Answer 1

的回答你的問題是正確的，你的錯誤消息。 :-)

這是告訴你，你認爲對象類型NSString真的NSArray。因此，NSArray不響應任何稱爲isEqualToString的方法。

在你的fetchUserName方法中，你將一個對象轉換爲NSString並返回它，但顯然你在這裏得到一個NSArray。當您將此對象設置爲標籤的文本屬性時，幕後會出現一些內容，詢問當前的字符串屬性是否與您嘗試設置的字符串屬性相同。然後，錯誤。

嘗試在fetchUserName方法把此行你return前：

NSLog(@"%@",username); 
return username; 

然後用這個的NSLog（）的控制檯結果修改您的問題，我們可以幫助你找出什麼是數組中。

好吧，你返回用戶名對象之前，這樣做：

NSString *username; 
id object = [recipient valueForKey:@"username"]; 
if ([object isKindOfClass:[NSString class]]) { 
    username = (NSString *)object; 
    return username; 
} else if ([object isKindOfClass:[NSArray class]]) { 
    NSArray *returnedArray = (NSArray *)object; 
    if (returnedArray.count > 0) { 
     id arrayMember = [returnedArray objectAtIndex:0]; 
     if ([arrayMember isKindOfClass:[NSString class]]) { 
      username = (NSString *)arrayMember; 
      return username; 
     } 
    } 
} 
return nil; 

Answer 2

您正在鑄造[recipientUser valueForKey:@"username"]作爲NSString以使您的代碼正常工作，但實際上它返回NSArray。刪除鑄(NSString*)並獲得代碼的工作，所以你實際上是從recipientUser拉字符串而不是數組。

要調試，我建議改變你的記錄到：

if ([fetchedUserNameObject objectAtIndex:0]!= NULL) 
{ 
    recipientUser = (User*)(fetchedUserNameObject); 
    NSArray *userNames = [recipientUser valueForKey:@"username"]; 
    for (int i=0; i < [userNames count]; i++) { 
     NSLog(@"Username %i is %@", i, [userNames objectAtIndex:i]); 
    } 
}