iOS: button in UITableViewCell class to call method on main UIViewController

Question

I have a UITableView on my MainViewController which has custom UITableCell s defined in a CustomCell class. I need an UIButton , which is in my CustomCell class, to call a method in MainViewController . I cannot create a new instance of MainViewController because the method uses some variables which would all be in the default state if I created a new instance. What do I do??

This is my code:

MainViewController.m (this is the method I want called):

-(void)updateLabels{
   double totalValue=0, personValue=0;
    [self returnTickArray];
    for(NSInteger i = 0; i < n; i++) {
        totalValue += ([[[self returnPricesArray] objectAtIndex:i] doubleValue] * [[[self returnQtyArray] objectAtIndex:i]doubleValue]);
        if([[[self returnPeopleArray] objectAtIndex:i]doubleValue]>0) personValue += ([[[self returnPricesArray] objectAtIndex:i] doubleValue] * [[[self returnQtyArray] objectAtIndex:i]doubleValue]/ [[[self returnPeopleArray] objectAtIndex:i]doubleValue] * [[[self returnTickArray] objectAtIndex:i]doubleValue]);
    }
    _totalValue.text = [NSString stringWithFormat:@"$ %.02lf", totalValue];
    _tip.text= [NSString stringWithFormat:@"$ %.02lf", totalValue*(([_tipPercentage.text doubleValue]/100))];
    _addedValue.text= [NSString stringWithFormat:@"$ %.02lf",([[_tip.text substringFromIndex:2] doubleValue]+totalValue) ];
    _perPerson.text=[NSString stringWithFormat:@"$ %.02lf", personValue];
}

This is the method in CustomCell.m which gets called when I press the button:

- (IBAction)tick:(UIButton *)sender {

    if ([sender isSelected]) {
        [sender setImage:[UIImage imageNamed:@"off"] forState:UIControlStateNormal];
        [sender setSelected:NO];
        _isTicked = [NSNumber numberWithInt:0];
    }
    else {
        [sender setImage:[UIImage imageNamed:@"on"] forState:UIControlStateSelected];
        [sender setSelected:YES];
        _isTicked = [NSNumber numberWithInt:1];
    }

}

Answer 1

you can assign a method from your controller to a button from UITableView in your - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath method

[cell.yourButton addTarget:self action:@selector(updateLabels) forControlEvents:UIControlEventTouchUpInside];

(just don't forget to add IBOutlet of your button to your custom cell class)

Answer 2

Handling changes, actions, or user interaction in other views is the essential use case of delegates . The best practice is to have the MainViewController be the delegate of the CustomCell , and then as events happen in the cell (ie, tick is called), it calls certain methods on its delegate to notify it and the delegate then calls updateLabels .

Other options for keeping values/state in sync between views are:

• Core Data - best used for data
• Key-Value Observation - best used for data
• NSNotification s sent through NSNotificationCenter - best used for actions

Answer 3

interesting :) You need to use [UIApplication sharedApplication] singleton to process this. Here are few steps:

Create object of MainViewController In you AppDelegate class:

in AppDelegate.h import MainViewController.h

@interface AppDelegate
{
    MainViewController *mvc;
}
@property (strong) MainViewController *mvc;

in MainViewController.m

@implementation AppDelegate

@synthesize mvc =_mvc

Now come to your CustomCell.m

- (IBAction)tick:(UIButton *)sender {

    [[(AppDelegate *)[[UIApplication sharedApplication] delegate] hvc] tick:sender];
}

Here you are seeing a method is called- tick_fromCell: . Now you have to define this method in your MainViewController class' .h ans .m files.

in MainViewController.h

-(void)tick:(id)sender;

and in MainViewController.m

-(void)tick:(id)sender {

    NSLog("Clicking from my CustomCell :)");// Here you will put updateLabels method
    [self updateLabels];
}