How to set the width of a cell in a UITableView in grouped style

A better and cleaner way to achieve this is subclassing UITableViewCell and overriding its -setFrame: method like this:

- (void)setFrame:(CGRect)frame {
    frame.origin.x += inset;
    frame.size.width -= 2 * inset;
    [super setFrame:frame];
}

Why is it better? Because the other two are worse.

1. Adjust table view width in -viewWillAppear:

   First of all, this is unreliable, the superview or parent view controller may adjust table view frame further after -viewWillAppear: is called. Of course, you can subclass and override -setFrame: for your UITableView just like what I do here for UITableViewCells. However, subclassing UITableViewCells is a much common, light, and Apple way.

   Secondly, if your UITableView have backgroundView, you don't want its backgroundView be narrowed down together. Keeping backgroundView width while narrow down UITableView width is not trivial work, not to mention that expanding subviews beyond its superview is not a very elegant thing to do in the first place.

2. Custom cell rendering to fake a narrower width

   To do this, you have to prepare special background images with horizontal margins, and you have to layout subviews of cells yourself to accommodate the margins. In comparison, if you simply adjust the width of the whole cell, autoresizing will do all the works for you.

If nothing works you can try this

Make the background colour of the cell as clear color and then put an image of the cell with required size. If you want to display some text on that cell put a label above the image. Don't forget to set the background color of the label also to clear color.

I found the accepted solution didn't work upon rotation. To achieve UITableViewCells with fixed widths & flexible margins I just adapted the above solution to the following:

- (void)setFrame:(CGRect)frame {

    if (self.superview) {
        float cellWidth = 500.0;
        frame.origin.x = (self.superview.frame.size.width - cellWidth) / 2;
        frame.size.width = cellWidth;
    }

    [super setFrame:frame];
}

The method gets called whenever the device rotates, so the cells will always be centered.

To do this in Swift, which does not provide methods to set variables, you'll have to override the setter for frame. Originally posted (at least where I found it) here

override var frame: CGRect {
    get {
        return super.frame
    }
    set (newFrame) {
        let inset: CGFloat = 15
        var frame = newFrame
        frame.origin.x += inset
        frame.size.width -= 2 * inset
        super.frame = frame
    }
}