Table view cell properties remain nil

Question

I am trying to implement the concept shown in this example project. My goal is to separate my view controller class and the datasource protocol. Instead of implementing the table view datasource methods in my table view controller class, I try to put it in its own class, and in my view controller, I only call this method to set up my table view:

- (void)setupTableView
{
    void (^configureCell)(JVRTodoItemCell *, JVRTodoItem *) = ^(JVRTodoItemCell *cell, JVRTodoItem *todoItem)
    {
        [cell configureForTodoItem:todoItem];
    };

    NSArray *todoItems = currentUser.todoItems;
    self.todoArrayDataSource = [[JVRArrayDataSource alloc] initWithItems:todoItems withCellIdentifier:TodoCellIdentifier withConfigureCellBlock:configureCell];
    self.tableView.dataSource = self.todoArrayDataSource;
    [self.tableView registerClass:[JVRTodoItemCell class] forCellReuseIdentifier:TodoCellIdentifier];
}

The data source is separated into its own class:

@interface JVRArrayDataSource ()

@property (copy,nonatomic) NSArray *items;
@property (copy,nonatomic) NSString *cellIdentifier;
@property (copy,nonatomic) void (^configureCellBlock)(id item, id cell);

@end

@implementation JVRArrayDataSource

...

#pragma mark - UITableViewDataSource

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return self.items.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:self.cellIdentifier forIndexPath:indexPath];
    id item = [self itemAtIndexPath:indexPath];
    self.configureCellBlock(cell,item);
    return cell;
}

The interesting part is that creating the cell based on the identifier (using dequeueReusableCellWithIdentifier:forIndexPath:) seems to be successful, because the correct cell gets allocated, but its labels remain nil. I try setting up my cell using the following method, but the values remain nil (aTodoItem has valid properties):

- (void)configureForTodoItem:(JVRTodoItem *)aTodoItem
{
    self.todoItemTitle.text = aTodoItem.title;
    self.todoItemPriority.text = [NSString stringWithFormat:@"%d", aTodoItem.priority];
} 

I am trying to figure out what could possibly be missing here, but so far, I haven't managed to fix the issue yet, and I'm starting to lose hope. Any help would be appreciated.

UPDATE: To make it clear, the issue is shown on this picture.

It seems that the cells get created, but its labels don't.

Answer 1

In the ViewDidLoad register the nib, it fix the problem :)

  -(void)viewDidLoad
    {
         [self.leftTableView registerNib:[UINib nibWithNibName:NIB_FILE bundle:nil] forCellReuseIdentifier:CELL_IDENTIFIER];
    }

Answer 2

After hours of digging, I've managed to solve the issue (for now), by changing my custom cell's outlets to strong properties, and initializing them in the cell's init method:

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    if (self) {
        self.todoItemTitle = [[UILabel alloc] init];
        self.todoItemPriority = [[UILabel alloc] init];
    }
    return self;
}

This is very strange, since I thought that creating my views in storyboard, this should be automatically taken care of, and I've never had to do this manually before.

Answer 3

If all you want to do is separate your tableview datasource delegate from the view controller you can create a separate class called TableViewDataSource. Within that class you can manage the datasources and their table view cells; configuring the them in your view controller, but letting the TableViewDataSource manage them.

TDSTableViewDataSource.h

#import <Foundation/Foundation.h>

@protocol TDSTableViewDataSourceDelegate <NSObject>

- (NSString *)fetchCellIdentifierForObject:(id)object;
- (UITableViewCell *)configureCell:(UITableViewCell *)cell usingObject:(id)item;

@end

@interface TDSTableViewDataSource : NSObject <UITableViewDataSource>

@property (strong, nonatomic) NSArray *items;
@property (strong, nonatomic) id<TDSTableViewDataSourceDelegate> delegate;

@end

TableViewDataSource.m

#import "TDSTableViewDataSource.h"

@implementation TDSTableViewDataSource

- (NSArray *)items {
    if (!_items) _items = [[NSArray alloc] init];
    return _items;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    if ([self.items count]) {
        return [self.items count];
    } else {
        NSLog(@"numberOfSectionsInTableView could not be determined. self.items is nil or empty.");
        return 0;
    }
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    if ([self.items count]) {
        return [self.items count];
    } else {
        NSLog(@"numberOfRowsInSection could not be determined. self.items contains fewer section requested does not contain any items.");
        return 0;
    }
}

/*
 Single dimension Array of items belonging to a UITableView section

 The method checks if the cell implements the HZConfigureTableViewCellDelegate, which is required.
 The delegate should be the View Controller.
 */
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    id obj = [self.items objectAtIndex:indexPath.row];
    UITableViewCell *cell = nil;

    if ([self.delegate conformsToProtocol:@protocol(TDSTableViewDataSourceDelegate)]) {
        NSString *cellIdentifier = [self.delegate fetchCellIdentifierForObject:obj];
        cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

        if (obj)
            cell = [self.delegate configureCell:cell usingObject:obj];
    }

    return cell;
}

@end

This class and the protocol will essentially allow you to fetch and configure UITableViewCell's and not have to implement the protocols into your View Controller.

Inside your view controller, you create a datasource property using the protocol above.

#import "TDSViewController.h"
#import "TDSTableViewDataSource.h"

@interface TDSViewController () <UITableViewDelegate, TDSTableViewDataSourceDelegate>
@property (strong, nonatomic) TDSTableViewDataSource *dataSource; // UITableView data source.
@property (weak, nonatomic) IBOutlet UITableView *tableView;
@end

@implementation TDSViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.tableView.dataSource = self.dataSource;
    self.dataSource.delegate = self;
}

#pragma mark - UITableView methods
-(NSString *)fetchCellIdentifierForObject:(id)object {
    // Check if this is an event or a Reminder class.
    if ([object isKindOfClass:[UITableViewCell class]]) {
        // Return the cell identifier for this particular cell.

        return @"com.myapp.defaultcell";
    }

    return @"blankcell";
}

- (UITableViewCell *)configureCell:(UITableViewCell *)cell usingObject:(id)item {
    UITableViewCell *configuredCell = cell;

    // Check if this is an event or a reminder.
    if ([item isKindOfClass:[UITableViewCell class]]) {
        // Configure the cell to present what data we want here...

    }

    return configuredCell;
}

@end

This is a complete example project. You can use this to configure any kind of cell you want, without having to add the datasource methods to your view controllers.

The view controller is used by the ConfigureTableViewCellDelegate protocol to configure the UITableViewCell's and use them in the Table View. Since the code is segregated now, the TableViewDataSource class now handles presenting the data to the table view. The View Controller is simply used to configure the cell's. This allows you to use custom UITableViewCells' on each ViewController if you want, and not have to deal with implementing the data sources each time.

UPDATED

Provided a better example, a complete project template.