Question

I have a UIViewController that I plan to have two TableViews and some other items in.
Both TableViews I am using on other screens, so I want to make them as independent and reusable as possible. One of those TableViews is called messageList (A UITableView) which shows my ChatHistory.

I am trying to understand if my approach is. [Edited 9/2 with correct code to make this approach work]

One approach would be to use a single table with 2 different sections, then in the delegate methods use a conditional statement to see which section is which and act accordingly.

The problem with this approach is usability. I want to easily reuse my TableViews in other views where one or the other TableView may or may not exist. Additionally, I want the DataSource to exist throughout the lifecycle of the app regardless of what Controller is instantiated or active.

My approach is to separate the view controller that manages the table view’s from the table UITableViewDataSource and UITableViewDelegate implementations. But I am having a problem making this work.

Focusing on one of the TableViews, my ChatTableView.

In my AppDelegate has a property for chatHistory of type ChatHistory which implements UITableViewDelegate & UITableViewDataSource.

// AppDelegate.h

ChatHistory *chatHistory;
...
@property (nonatomic, retain) ChatHistory *chatHistory;

// ChatHistory.h

#import <Foundation/Foundation.h>

@interface ChatHistory : NSObject <UITableViewDelegate, UITableViewDataSource> {
    UITableViewCell *nibLoadedCell;
    NSMutableArray *messages;
}
@property (nonatomic, retain) UITableViewCell   *nibLoadedCell;
@property (nonatomic, retain) NSMutableArray    *messages;

@end

// ChatHistory.m – Note this code, including the custom cell was working correctly when it was a part of the controller so I believe it should be correct

#import "ChatHistory.h"
#include "ChatMessage.h"

@implementation ChatHistory
@synthesize nibLoadedCell;   // custom cell design
@synthesize messages;

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return 1;
}

- (NSInteger)tableView:(UITableView *)tableView 
 numberOfRowsInSection:(NSInteger)section {
return [messages count];
}

- (NSString *)tableView:(UITableView *)tableView
titleForHeaderInSection:(NSInteger)section {
return [NSString stringWithFormat:@"Discussion"];

}

- (UITableViewCell *)tableView:(UITableView *)tableView
         cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (cell == nil) {
    [[NSBundle mainBundle] loadNibNamed:@"ChatTableCell" owner:self options:nil];
    cell = nibLoadedCell;
    }
    // custom tag order - username; message; future - Avatar; like; dislike
ChatMessage *obj = [messages objectAtIndex:indexPath.row];
UILabel *messageLabel = (UILabel *) [cell viewWithTag:1];
messageLabel.text = obj.message;
UILabel *usernameLabel = (UILabel *)[cell viewWithTag:2];
usernameLabel.text = obj.sender;
return cell;
}

- (void)dealloc {
    if (messages) [messages release];
    [super dealloc];
}
@end

// MyViewController.m

- (void)viewDidLoad {   // MAKE SURE TO INITIALIZE viewDidLoad not InitWithNib
        if (!appDelegate.chatHistory)
                appDelegate.chatHistory = [[ChatHistory alloc] init];

        messageList = [[UITableView alloc] initWithFrame:CGRectMake(0, 54, 320, 100) style:UITableViewStylePlain];
        messageList.dataSource = appDelegate.chatHistory;
        messageList.delegate = appDelegate.chatHistory;
        [self.view addSubview:messageList];
        ...

Answer 1

If you want one central data store, you could create a Singleton class with the data.
Then set it as the data source for the table view or fetch the array (or whatever you got) from the data store in your UIViewController / UITableViewController.

If you initialize the data store in your AppDelegate, you can access it from every class you want (note that all data you load, will remain in memory until your application gets terminated by iOS)

How to create a Singleton class in Objective-C