add messagesInConversation for ordered messages

Yep/Realm/Models.swift

@@ -185,4 +185,9 @@ func tryGetOrCreateMe() -> User? {
     return nil
 }
 
+func messagesInConversation(conversation: Conversation) -> RLMResults {
+    let predicate = NSPredicate(format: "conversation = %@", conversation)
+    let messages = Message.objectsWithPredicate(predicate).sortedResultsUsingProperty("createdAt", ascending: true)
+    return messages
+}
 

Yep/ViewControllers/Conversation/ConversationViewController.swift

@@ -7,11 +7,15 @@
 //
 
 import UIKit
+import Realm
 
 class ConversationViewController: UIViewController {
 
     var conversation: Conversation!
-    
+
+    lazy var messages: RLMResults = {
+        return messagesInConversation(self.conversation)
+        }()
 
     @IBOutlet weak var conversationCollectionView: UICollectionView!
 
@@ -174,7 +178,7 @@ extension ConversationViewController: UICollectionViewDataSource, UICollectionVi
 
     func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
 
-        let message = conversation.messages[indexPath.row]
+        let message = messages.objectAtIndex(UInt(indexPath.row)) as! Message
 
         if let sender = message.fromFriend {
             if sender.friendState != UserFriendState.Me.rawValue {
@@ -220,7 +224,7 @@ extension ConversationViewController: UICollectionViewDataSource, UICollectionVi
 
         // TODO: 缓存 Cell 高度才是正道
         // TODO: 不使用魔法数字
-        let message = conversation.messages[indexPath.row]
+        let message = messages.objectAtIndex(UInt(indexPath.row)) as! Message
 
         let rect = message.textContent.boundingRectWithSize(CGSize(width: messageTextLabelMaxWidth, height: CGFloat(FLT_MAX)), options: .UsesLineFragmentOrigin | .UsesFontLeading, attributes: messageTextAttributes, context: nil)
 

Yep/Views/Cells/Conversation/ConversationCell.swift

@@ -42,7 +42,7 @@ class ConversationCell: UITableViewCell {
                     }
                 }
 
-                if let latestMessage = conversation.messages.last {
+                if let latestMessage = messagesInConversation(conversation).lastObject() as? Message {
                     self.chatLabel.text = latestMessage.textContent
                     self.timeAgoLabel.text = "\(latestMessage.createdAt)"
                 } else {
@@ -59,7 +59,7 @@ class ConversationCell: UITableViewCell {
                 self.nameLabel.text = ""
             }
 
-            if let latestMessage = conversation.messages.last {
+            if let latestMessage = messagesInConversation(conversation).lastObject() as? Message {
                 if let messageSender = latestMessage.fromFriend {
                     AvatarCache.sharedInstance.roundAvatarOfUser(messageSender, withRadius: radius) { roundImage in
                         dispatch_async(dispatch_get_main_queue()) {