過濾包含消息列表的NSMutableArray

我想過濾和排序包含聊天消息列表的NSMutableArray。我正在嘗試獲取2個用戶之間對話的最後消息。例如，如果user1與2個不同的用戶有2個不同的會話，我想要獲得每個會話的最後一個消息。我使用Parse.com作爲後端，並且這是我保存&檢索到的消息。過濾包含消息列表的NSMutableArray

保存消息

PFUser *user = [[PFUser currentUser] objectForKey:@"displayName"]; 
PFObject *newMessage = [PFObject objectWithClassName:@"Messages"]; 
[newMessage setObject:messageStr forKey:@"body"]; 
[newMessage setObject:self.mySelectedUser forKey:@"toUser"]; 
[newMessage setObject:user forKey:@"fromUser"]; 
[newMessage saveInBackground]; 
myMessageField.text = @""; 
[self getTheNewMessages]; 
[self.myTView reloadData];

檢索消息

-(void)GetmyNewMessages 

{ 
PFQuery *query1 = [PFQuery queryWithClassName:@"Messages"]; 
[query1 whereKey:@"toUser" equalTo:[[PFUser currentUser] objectForKey:@"displayName"]]; 
[query1 whereKeyExists:@"date"]; 

PFQuery *query2 = [PFQuery queryWithClassName:@"Messages"]; 
[query2 whereKey:@"fromUser" equalTo:[[PFUser currentUser] objectForKey:@"displayName"]]; 
[query2 whereKeyExists:@"date"]; 

PFQuery *query = [PFQuery orQueryWithSubqueries:[NSArray arrayWithObjects:query1, query2, nil]]; 

[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) { 
     if (!error) { 


      NSLog(@"Successfully retrieved %d chats.", objects.count); 
      [premessagesList removeAllObjects]; 
      [premessagesList addObject:objects]; 
    } else { 
      //Log details of the failure 
      NSLog(@"Error: %@ %@", error, [error userInfo]); 


     } 


    }];

}

的NSLog所述的NSMutableArray（premessageList）的

("<Messages:aS8tVIlsHc:(null)> {\n 
    body = hi;\n fromUser = cnn;\n toUser =FNC;\n  
    date = \"2012-09-19 02:40:29 +0000\";\n}", 

    "<Messages:CPCa6VBmf7:(null)> {\n 
body = hello;\n fromUser = FNC;\n toUser =cnn;\n 
date = \"2012-09-20 05:06:05 +0000\";\n}", 


    "<Messages:Jz1cILt18Y:(null)> {\n 

    body = whatsgood;\n fromUser = sleepy;\n toUser =cnn;\n 

    date =\"2012-09-20 05:06:05 +0000\";\n}", 

    "<Messages:lXretmE1uK:(null)> {\n 
    body = lol;\n fromUser = cnn;\n toUser =sleepy;\n 

date =\"2012-09-20 05:13:16 +0000\";\n}",

我試圖使用NSSortDescriptor和NSPredicate，但我得到了一個空的tableview。

來源

2012-09-25 Bill H

在這種類型的問題，我會用一些變量和快速迭代通過信息苦幹，讓你需要的東西：

id lastChat = ni; 
... temps 

for(OneChat in allChats) { 
    do tests and set variables 
} 

Now I know the last chat.

PS：我決定不發佈此，但是當我看到後，很長一段時間沒有人迴應過，認爲這比沒有好。這是我將如何解決這個問題。

來源

2012-09-26 00:23:36

你可以限制結果和排序通過PFQuery本身是這樣的：

[query1 orderByDescending:@"createdAt"]; 
query1.limit = 1; 
[query2 orderByDescending:@"createdAt"]; 
query2.limit = 1;

來源

2013-01-16 20:52:27 Bejmax

過濾包含消息列表的NSMutableArray

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