iOS - how to get access to a variable from the container view and pass it back to the view controller

Question

I've a 'viewContoller' VC1 and a container view in it with a table view controller embedded in VC1.

I've a variable called number which is adding up according to the didSelectRowAtIndexPath and deducting using didDeselectRowAtIndexRowPath since its a table.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    number += [[[self.sports objectAtIndex:indexPath.row] valueForKey:@"sportNumber"] intValue];
}

 -(void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath {
    number -= [[[self.sports objectAtIndex:indexPath.row] valueForKey:@"sportNumber"] intValue];
}

This "number" value belongs to the embedded table controller and I need to access it in VC1.

Additionally the "number" variable constantly changes according to it being selected or deselected and VC1 needs to know when this happens so it has the most updated value.

I've been looking for a solution for days, any help would be appreciated.

Answer 1

Sharing data between different classes can be done in various ways but the most cleaner way to do is to keep the shared data outside of all classes who are using/modifying this value by following the loosely coupled design. One can think of a Singleton class but that will be kind a overuse if we have only one property (value) which is being shared.In this case we can have a class with one internal static variable and class methods (with + sign) to access it. Here is the code for the same:

.h file--->
#import <Foundation/Foundation.h>

@interface SharedData : NSObject

+(void)resetNumber;
+(void)incrementNumber;
+(void)decrementNumber;
+(int)getNumber;
@end]

.m File --->

#import "SharedData.h"

@implementation SharedData

static int number;

+(void)resetNumber {
    number = 0;
}

+(void)incrementNumber {
    number++;
}

+(void)decrementNumber {
    number--;
}

+(int)getNumber {
    return number;
}


@end

Here is the usage of the class Use @class SharedData only to import it before @implementation

[SharedData incrementNumber]

Hope this might help you !!!!!

Answer 2

Simple, do as below,

1) Go to interface builder and set name to your segue of UIContainerView embed (let's say 'abc'). Later we are gonna access it from VC1(in step 4).

---

2) Define your number variable in VC1 header.

---

3) In table view controller header define a reference to your VC1 like this,

@property(nonatomic, retain) VC1 *VC;

---

4) In VC1 class, implement prepareForSegue and do as below,

- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    NSString * segueName = segue.identifier;
    if ([segueName isEqualToString: @"abc"]) {
        TableViewController *tblVC = (TableViewController *) [segue destinationViewController];
        tblVC.VC = self;
    }
}

5) Now in table view controller you can access your number variable like below,

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

if (self.VC) {
        self.VC.number += [[[self.sports objectAtIndex:indexPath.row] valueForKey:@"sportNumber"] intValue];
  }   
}

 -(void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath {

if (self.VC) {
    self.VC.number -= [[[self.sports objectAtIndex:indexPath.row] valueForKey:@"sportNumber"] intValue];
  }
}

Now you can access number variable from VC1 since it is defined in VC1 header. Remember this is just one way to achieve your requirement, There are several ways to handle this kind of situations. Such as, if you want you can do other way around too.

Answer 3

If I get your question correctly, you have a tableView inside a VC and you want to be updated when a user didSelect/DidDeselect a row.

An alternative solution will be having a protocol implementation.

@protocol SpecialTableViewFunctionDelegate <NSObject>

@optional
- (void)didSelectSomethingUpdatedNumber:(NSNumber *)number;
- (void)didDeselectSomethingUpdatedNumber:(NSNumber *)number;
@end

This is of course assuming you subclassed tableView.

On your tableView subclass you can add the delegate for example:

@interface tableviewSubclass :UITableView
@property (nonatomic, weak)id<SpecialTableViewFunctionDelegate>delegate;
@end

then on your did select method you can do something like:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
  number += [[[self.sports objectAtIndex:indexPath.row] valueForKey:@"sportNumber"] intValue];
  if(_delegate){
     if([_delegate respondsToSelector:(@selector(didSelectSomethingUpdatedNumber:)]){
        [_delegate didSelectSomethingUpdatedNumber:number];
     }
  }
}

- (void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath {
   number -= [[[self.sports objectAtIndex:indexPath.row] valueForKey:@"sportNumber"] intValue];
   if(_delegate){
      if([_delegate respondsToSelector:(@selector(didDeselectSomethingUpdatedNumber:)]){
         [_delegate didDeselectSomethingUpdatedNumber:number];
     }
   }
  }
}

then on your VC you just have to assign the delegate to self. tableViewInstance.delegate = self;

Dont forget to include the delegate to the header <SpecialTableViewFunctionDelegate>

This way you'll be notified when there is a select/deselect of cell