Adding properties to UIControls without subclassing

问题

I have embedded UIButtons in my TableViewCells. In order to track which cell the button belongs to, I would like to add an NSIndexPath property to UIButton. I do not want to subclass a UIButton. Is there a way I can do this with categories?

EDIT: I believe the idea of setting tags will not work if I have multiple sections in the table view. Another approach of accessing the button's superview's superview to determine the cell seems more like a hack. Looking for a cleaner way of doing this.

回答1:

There are several approaches. If you just really need a single number rather than a full index path, you can use setTag:. It's inflexible, but it's readily available.

The next best solution is associative references. These can hang data onto any object, with proper memory management. I usually create a category that adds a property implemented using objc_setAssociatedObject and objc_getAssociatedObject.

回答2:

You can find out which cell a clicked button was in without having to associate tags or index paths with the buttons, which can get messy when re-using cells. Tags do work with sectioned tables but you have to mess about with numbers, e.g. 10001 is section 1, row 1, so you've got to convert at one end and convert back at the other, too fragile for my liking.

A nicer method is to use UITableView's indexPathForRowAtPoint: method. When your button's action is activated (assuming the target is in your table view controller:

CGPoint point = [sender convertPoint:sender.center toView:self.tableView];
NSIndexPath *path = [self.tableView indexPathForRowAtPoint:point];

sender here is cast to UIButton.

回答3:

In order to track which cell the button belongs to

You already know which cell the button belongs to: it's the cell that the button is a subview of.

Start with a reference to the button. (If you are the button, this is self. If you're the button's target for its action, then when the button is tapped and emits an action message, it passes itself along as parameter to the action message, usually called sender.)

Look up the view hierarchy (superview) to find the UIViewTableCell containing the button.

UIView* v = theButton;
while (![v isKindOfClass: [UITableViewCell class]]) v = v.superview;

Now you can do whatever you like with that info. For example, you seem to want an NSIndexPath; then call -[UITableView indexPathForCell:].

来源：https://stackoverflow.com/questions/8492602/adding-properties-to-uicontrols-without-subclassing

标签

objective-c

ios

uicontrol