Question

In the tableView:cellForRowAtIndexPath: implementation of my UITableViewController subclass I’m using this code snippet:

AlarmPicker *alarmPicker = [[AlarmPicker alloc] init];
alarmPicker.scrollViewDelegate = alarmPicker;
[cell.contentView addSubview:alarmPicker.view];

AlarmPicker implements various UIScrollViewDelegate methods.

In AlarmPicker.h I’m declaring scrollViewDelegate as follows:

@property (assign) id<UIScrollViewDelegate> scrollViewDelegate;

This is then being used in the implementation part of AlarmPicker:

UIScrollView *returnScrollView = [[UIScrollView alloc] init];
...
returnScrollView.delegate = self.scrollViewDelegate;

Unfortunately scrollViewDelegate is always null in this AlarmPicker instance so the implemented delegate methods don’t get called at all.

A workaround would be to put the UIScrollViewDelegate method implementations into the class which does the alloc and init:

...
alarmPicker.scrollViewDelegate = self;
...

But that would be a very bad solution.

What do I have to do in order to tell the AlarmPicker instance that it should use itself as its delegate?

Answer 1

Is there some reason that you can’t just write returnScrollView.delegate = self in your AlarmPicker class?

I don’t see any reason why your scrollViewDelegate member would be nil here, unless the line returnScrollView.delegate = self.scrollViewDelegate; is happening in your init method, in which case you could move it to a later method or pass the required delegate in your AlarmPicker’s init method.