How to track tableview cell's textfield text from viewcontroller?

Question

I would like to observe changes in tableview-cell-textfield's text from related view controller.

I have a text field inside of a cell. It conforms to protocol named 'RouteChangesInfoTableViewCellDelegate'

@protocol RouteChangesInfoTableViewCellDelegate 
@required
- (void)textFieldDidChange:(NSString *)textNote;
@end

Related cell conforms to that protocol.

@interface RouteChangesInfoTableViewCell : UITableViewCell

Inside of cell's protocol function I am delegating related text without calling.

- (void)textFieldDidChange:(nonnull NSString *)textNote {
    [_routeChangesInfoDelegate textFieldDidChange:self.txtNote.text];
}

Related viewcontroller also conforms to the protocol

@interface RouteChangesInfoViewController : UIViewController


Inside of viewcontroller  I am trying to delegate as below
- (UITableViewCell *)tableView:(nonnull UITableView *)tableView cellForRowAtIndexPath:(nonnull NSIndexPath *)indexPath {
    RouteChangesInfoTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"RouteChangesInfoTableViewCell" forIndexPath:indexPath];
    [cell setRouteChangesInfoDelegate:self];
    return cell;
}

Inside of viewcontroller  I am trying to log texts but nothing happens.
- (void)textFieldDidChange:(nonnull NSString *)textNote {
    NSLog(@"DEBUG %@:", textNote);
}


Is this delegation pattern is right?
If I would like to observe related text change how can I implement the observer (to where)

Thank you!

DonMag · Accepted Answer

You don't quite have the protocol/delegate pattern understood.

You define the protocol correctly:

@protocol RouteChangesInfoTableViewCellDelegate 
@required
- (void)textFieldDidChange:(NSString *)textNote;
@end

but then you're setting your cell class to conform to that delegate. That's not what you want.

You need to create a delegate property in your cell class. Your View Controller will conform to that delegate, and then set the delegate property of the cell to self (the VC).

Then connect an - (IBAction)textFieldDidChange:(id)sender in your cell class to the text field. When triggered, that is where you call the delegate method.

Here is a complete example...

RouteChangesInfoTableViewCell.h

//
//  RouteChangesInfoTableViewCell.h
//  Created by Don Mag on 8/29/20.
//

#import 

NS_ASSUME_NONNULL_BEGIN

@protocol RouteChangesInfoTableViewCellDelegate 
@required
- (void)textFieldDidChange:(NSString *)textNote;
@end

@interface RouteChangesInfoTableViewCell : UITableViewCell

@property (nonatomic, weak) id  routeChangesInfoDelegate;

@end

NS_ASSUME_NONNULL_END

RouteChangesInfoTableViewCell.m

//
//  RouteChangesInfoTableViewCell.m
//  Created by Don Mag on 8/29/20.
//

#import "RouteChangesInfoTableViewCell.h"

@implementation RouteChangesInfoTableViewCell

- (IBAction)textFieldDidChange:(id)sender {
    UITextField *tf = (UITextField *)sender;
    [_routeChangesInfoDelegate textFieldDidChange:tf.text];
}

@end

RouteChangesInfoViewController.h

//
//  RouteChangesInfoViewController.h
//  Created by Don Mag on 8/29/20.
//

#import 

NS_ASSUME_NONNULL_BEGIN

@interface RouteChangesInfoViewController : UIViewController 

@end

NS_ASSUME_NONNULL_END

RouteChangesInfoViewController.m

//
//  RouteChangesInfoViewController.m
//  Created by Don Mag on 8/29/20.
//

#import "RouteChangesInfoViewController.h"
#import "RouteChangesInfoTableViewCell.h"

// conform to RouteChangesInfoTableViewCellDelegate
@interface RouteChangesInfoViewController () 

@property (strong, nonatomic) IBOutlet UITableView *tableView;

@end

@implementation RouteChangesInfoViewController

// delegate method
- (void)textFieldDidChange:(NSString *)textNote {
    NSLog(@"Got text from cell: %@", textNote);
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // make sure table view delegate and datasource are set
    _tableView.delegate = self;
    _tableView.dataSource = self;
    
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return 1;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    RouteChangesInfoTableViewCell *cell = (RouteChangesInfoTableViewCell *)[tableView dequeueReusableCellWithIdentifier:@"cell" forIndexPath:indexPath];
    
    // set the cell's delegate
    cell.routeChangesInfoDelegate = self;
    
    return cell;
}

@end

Storyboard with outlet connections...

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