Question

I have a view based table with a custom cell view. Inside this custom cell view, I have a custom NSButton that acts like a check box (it toggles a custom image on and off). This part works well. The images toggle on and off perfectly.

What I want to do is associate the custom button in the row with the actual row in the table. When I check/click the button it will highlight the the corresponding row and then perform an action on the row in which the check box/ button is situated. For example, removing the row from the table when the NSButton is clicked.

My custom NSButton is implemented as follows:

Header file:

#import <Foundation/Foundation.h>

@interface CustomCheckButton : NSButton {
    BOOL _checked;
}

@property (nonatomic, setter=setChecked:) BOOL checked;

-(void) setChecked:(BOOL) check;
@end

Implementation:

#import "CustomCheckButton.h"

@implementation CustomCheckButton

@synthesize checked = _checked;

-(id) init
{
    if( self=[super init] )
    {
        self.checked = NO;
        [self setTarget:self];
        [self setAction:@selector(onCheck:)];
    }
    return self;
}

-(void) awakeFromNib
{
    self.checked = NO;
    [self setTarget:self];
    [self setAction:@selector(onCheck:)];
}

-(void) setChecked:(BOOL) check
{
    _checked = check;
    if( _checked )
    {
        NSImage* img = [NSImage imageNamed:@"check_on.png"];
        [self setImage:img];
        [self setState:NSOnState];
    }
    else
    {
        NSImage* img = [NSImage imageNamed:@"check_off.png"];
        [self setImage:img];
        [self setState:NSOffState];
    }
}

-(void) onCheck:(id) sender
{
    self.checked = !_checked;
    NSLog(@"A check box was pressed");
}

@end

The current solution does not associate the button with the row at all. When I sort the rows, for example, the selected image is not linked to the row and often stays in the same place within the table, even though a different row was selected.

Any help on this would be greatly appreciated.

Answer 1

How about adding a delegate field and setting it with a custom initializer? Or you could add it as a property and set it after calling alloc init. This can be done in 2 ways: via IB or programmatically.

If you want to do it programmatically, you’ll need to do a couple of things:

So let’s look at the class that has a UITableView element in it. Assuming this class is also the UITableViewDelegate and UITableViewDataSource, it will have to have an implementation of the data source method

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath;

which returns a cell at a given indexPath. Here, you could instantiate your custom cell and in that, add a custom button and set it’s delegate to the cell itself, by adding this to your code:

in CustomCheckButton.h:

UITableViewCell * delegate;
//...
@property (nonatomic, assign) UITableViewCell * delegate;

in CustomCheckButton.m

@synthesize delegate;

in the table view data source method:

// initialize my custom cell element, assume it has a property for a CustomCheckButton with name checkButton
// ... some code
myCell.checkButton.delegate = mycell; // link the button's delegate to the cell
// ... some other code, probably based on indexPath
return myCell;

This might seem like a big task, but you can do it in interface builder too, assuming you have a xib for your custom cell class. If you do, just open the xib. You’ll probably have a button on it already; change it’s class to your own CustomCheckButton and you’ll be able to set its delegate property like you would normally, with ctrl-drag from the button to the cell.

Hope this helps!