CODEWITHSUNDEEP
iosobjective-cuitableviewstatic
Josh Kahane
Josh Kahane

Reputation: 17169

Static UITableView Cell Property Modification

I have a static UITableView setup in my storyboard. I have subclassed some cells and added this property:

@property (nonatomic, strong) UILabel *label;

I also have code to add the label to my cell in the layoutSubviews method. My label shows in my cell without an issue. I can see the label saying 'PLACEHOLDER' but it is not updated to say the text I set in cellForRowAtIndexPath.

In the cellForRowAtIndexPath method, I have the following:

APInfoTableViewCell *cell = (APInfoTableViewCell*)[super tableView:tableView cellForRowAtIndexPath:indexPath];

[cell.label setText@"Hello World"];

However, this will not update the text in my label. The label is actually nil.

EDIT:

Here is the full code...

UITableViewCell Subclass:

@property (nonatomic, strong) UILabel *infoLabel;

-(void)layoutSubviews
{
    [super layoutSubviews];

    [self initUI];
}

-(void)initUI
{
    //add long press to show info label
    _infoLabel = [UILabel new];
    [_infoLabel setText:@"PLACEHOLDER"];
    [_infoLabel setFont:[UIFont fontWithName:@"Avenir-Medium" size:10.0f]];
    [_infoLabel setTextAlignment:NSTextAlignmentCenter];
    [_infoLabel setTextColor:[UIColor apText]];
    [_infoLabel setAlpha:1.0f];
    [_infoLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
    [self addSubview:_infoLabel];

    NSArray *infoConstraintH = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-40-[infoLbl]-40-|" options:0 metrics:nil views:@{ @"infoLbl" : _infoLabel }];
    [self addConstraints:infoConstraintH];
    NSArray *infoConstraintV = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[infoLbl]-10-|" options:0 metrics:nil views:@{ @"infoLbl" : _infoLabel }];
    [self addConstraints:infoConstraintV];
}

ViewController:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    APInfoTableViewCell *cell = (APInfoTableViewCell*)[super tableView:tableView cellForRowAtIndexPath:indexPath];

[cell.infoLabel setText@"Hello World"];

return cell;
}

Upvotes: 0

Views: 47

Answers (2)

Nicholas H.
Nicholas H.

Reputation: 1311

You need to instantiate a new cell in tableView:cellForRowAtIndexPath: or use dequeueReusableCellWithIdentifier:. cellForRowAtIndexPath: returns visible instantiated cells in the table view. As you aren't instantiating your cells anywhere there are no cells in the table view, so cellForRowAtIndexPath: returns nil.

Additionally layoutSubviews is called a lot and is called late. You should not rely on it to initialise your label. As it stands your cell will keep adding additional labels when ever layoutSubviews is called! The designated initialiser is the place to add that initUI code (as the name implies 😉). If your UITableViewCell subclass doesn't use a XIB/Storyboard for its view, initWithStyle:reuseIdentifier: is the designated initialiser. (Otherwise it is initWithCoder: or awakeFromNib)

Upvotes: 0

Johnykutty
Johnykutty

Reputation: 12839

If you are using storyboard, and you don't want to add IB outlet then call your initUI method from awakeFromNib method. If you are not using storyboard implement - (instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier method and call it from there.

awakeFromNib method is called once the cell(or any UIView subclass) is instantiated from nib(either from storyboard or from xib). And its called only once in the lifetime of the view

Note: This will not get called if you are creating a view subclass programmatically.

As per documentation

Subclasses can override this method as needed to perform more precise layout of their subviews. You should override this method only if the autoresizing and constraint-based behaviors of the subviews do not offer the behavior you want. You can use your implementation to set the frame rectangles of your subviews directly.

That means, use this method to do any additional lay outing of already added. This method is called when some frame/autolayout constraint changes happens.

Upvotes: 1

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