排序使用NSSortDescriptor不工作

Question

我有一個數組unsortedPosts滿字典，它看起來是這樣的，如果我在終端內容打印出來NSDictionaries的NSArray的：

{ 
    "created_at" = 1332584959; 
    id = "61926802418418"; 
    network = "net1"; 
    text = "text1"; 
    url = "https://www.google.com"; 
}, 
{ 
    "created_at" = 1332581096; 
    id = "6192689218418"; 
    network = "net1"; 
    text = "text1"; 
    url = "https://www.yahoo.com"; 
}, 
{ 
    "created_at" = 1332581074; 
    id = "6192688628418"; 
    network = "net1"; 
    text = "text1"; 
    url = "https://www.aol.com"; 
} 

我想通過created_at場對它們進行排序（unix時間戳）。我正在使用NSSortDescriptor，如下所示：

NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"\"created_at\"" ascending:TRUE]; 
NSMutableArray *sortDescriptors = [NSMutableArray arrayWithObject:sortDescriptor]; 
NSArray *sortedSocialPosts; 
sortedSocialPosts = [unsortedSocialPosts sortedArrayUsingDescriptors:sortDescriptors]; 

但輸出未排序。

編輯

我試圖運行它，而無需使用周圍created_at轉義引號（每@Eimantas答案）：

NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"created_at" ascending:TRUE]; 
NSMutableArray *sortDescriptors = [NSMutableArray arrayWithObject:sortDescriptor]; 
NSArray *sortedSocialPosts; 
sortedSocialPosts = [unsortedSocialPosts sortedArrayUsingDescriptors:sortDescriptors]; 

但我得到這個錯誤：

-[__NSCFNumber length]: unrecognized selector sent to instance 0x6a2a3c0 
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFNumber length]: unrecognized selector sent to instance 0x6a2a3c0' 

Answer 1

你不需要逃脫的報價，只需通過@"created_at"，你就會很好。有時會在打NSLog()調用時打印報價。我非常肯定，您只需訪問@"created_at"密鑰和valueForKey:方法即可訪問創建時間戳。

更新

這可能意味着一些created_at值可能是NSString實例和一些 - NSNumber實例。你能否確認所有的created_at值是同一類型的？ （使用NSLog(@"%@", [[unsortedSocialPosts valueForKey:@"created_at"] valueForKey:@"class"]);