錯誤：使用日期和時間屬性對NSMutableArray對象進行排序？

Question

我正在處理聊天類應用程序。在哪裏我從服務器獲取完整的消息列表並將其保存到自定義實體NSObject類的數組中。

這裏是我的class.h：

進口

@interface ChatMessage : NSObject 

@property (nonatomic, retain) NSString *msg_text; 
@property (nonatomic, retain) NSDate *msg_date; 
@property (nonatomic, assign) int sender_id; 
@property (nonatomic, assign) int receiver_id; 
@property (nonatomic, retain) NSString *msg_status; 

@end 

這裏是我的class.m：

#import "ChatMessage.h" 

@implementation ChatMessage 

@synthesize msg_text, msg_date, msg_status, sender_id, receiver_id; 

- (id) initWithCoder: (NSCoder *)coder 
{ 
    self = [[ChatMessage alloc] init]; 
    if (self != nil) 
    { 
     self.msg_text = [coder decodeObjectForKey:@"msg_text"]; 
     self.msg_date = [coder decodeObjectForKey:@"msg_date"]; 
     self.msg_status = [coder decodeObjectForKey:@"msg_status"]; 
     self.sender_id = [coder decodeIntForKey:@"sender_id"]; 
     self.receiver_id = [coder decodeIntForKey:@"receiver_id"]; 
    } 
    return self; 
} 

- (void)encodeWithCoder: (NSCoder *)coder 
{ 
    [coder encodeObject:msg_text forKey:@"msg_text"]; 
    [coder encodeObject:msg_date forKey:@"msg_date"]; 
    [coder encodeObject:msg_status forKey:@"msg_status"]; 
    [coder encodeInt:sender_id forKey:@"sender_id"]; 
    [coder encodeInt:receiver_id forKey:@"receiver_id"]; 
} 

@end 

我想要做的對象的排序NSMutableArray在我的CellForRowAtIndexPath中使用「msg_date」屬性，然後將其顯示到我的聊天列表表格視圖中。我爲每個聊天消息獲取日期和時間格式爲「2014-08-21 18:30:00」。

這裏是我的分選對象的數組代碼：

NSMutableArray *unsortedArray = [[NSMutableArray alloc] init]; 

//sorting array with date and time 
for (int i=0; i<[self.arrayChatMessages count]; i++) { 

ChatMessage *chat = [[ChatMessage alloc] init]; 
chat = [self.arrayChatMessages objectAtIndex:i];       

[unsortedArray addObject:chat.msg_date]; 
} 

NSLog(@"un sorted array is = %@", unsortedArray); 

NSArray *sortedArray = [unsortedArray sortedArrayUsingComparator:^(id obj1, id obj2) { 
            return [obj2 compare:obj1]; 
           }]; 

NSLog(@"sorted array is = %@", sortedArray); 

它成功地排序。在我的控制檯我得到：

un sorted array is = (
    "2014-08-21 18:28:58", 
    "2014-08-21 18:27:41", 
    "2014-08-21 20:10:45", 
    "2014-08-21 18:30:45", 
    "2014-08-29 12:27:45" 
) 

sorted array is = (
    "2014-08-29 12:27:45", 
    "2014-08-21 20:10:45", 
    "2014-08-21 18:30:45", 
    "2014-08-21 18:28:58", 
    "2014-08-21 18:27:41" 
) 

我的問題是根據這個排序的數組，我怎麼可以排序的對象即self.arrayChatMessages的陣列。

Answer 1

要排序自定義對象的NSArray，您可以使用-sortedArrayUsingComparator:方法，靠NSString的-compare:方法的結果是：

self.arrayChatMessages = [self.arrayChatMessages sortedArrayUsingComparator:^(ChatMessage *obj1, ChatMessage *obj2) { 
    return [obj1.msg_date compare:obj2.msg_date]; 
}]; 

此外，我會建議使用NSDateFormatter從NSString轉換你棗業的NSDate。