Duplicate code in UIScrollViewDelegate methods - ios

Question

I having recently implemented a solution that allows me to know when a scroll view has finished scrolling. This is so that when I scroll my tableview I only call a specific method once the tableview has stopped moving completely.
I followed the answer provided here :https://stackoverflow.com/a/8010066/2126233 but am including code below for ease of reading:
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
self.isScrolling = YES;
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
//[super scrollViewDidEndDragging:scrollView willDecelerate:decelerate]; // pull to refresh
if(!decelerate) {
self.isScrolling = NO;
[self callMethodThatRequiresTableViewAndArrayOfDataToBePassedIn];
}
}
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
self.isScrolling = NO;
[self callMethodThatRequiresTableViewAndArrayOfDataToBePassedIn];
}
- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView
{
self.isScrolling = NO;
}
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
{
self.isScrolling = NO;
}
This solution works perfectly. However I require this same logic in 4 different view controllers and I don't like having duplicate code.
I am unsure how I can implement the code above in one class and then use it in the other 4 classes.
I have had a few ideas:
I have a base class that all other view controllers inherit from. I was thinking I could subclass the base class and then the 4 view controls that require this code are subclassed from this new class. This new class provides the implementation for the scroll delegate methods. But how do I call the method and passing in the tableView and dataArray.
Subclassing UITableView and in the subclass implementing these 4 methods. This means I could pass in the tableView ok. But the data source is array is a little more problematic.
Does anyone have any suggestions on an elegant way this issue can be solved. Many thanks

Answer 1

I think you are on right track
I have a base class that all other view controllers inherit from. I was thinking I could subclass the base class and then the 4 view controls that require this code are subclassed from this new class. This new class provides the implementation for the scroll delegate methods.
Now your question is
how do I call the method and passing in the tableView and dataArray
For this you can take help of delegate methods
In your base class make a protocol
In yourBaseClass.h
#protocol MyDelegate <NSObject>
#required
-(void)callMethodThatRequiresTableViewAndArrayOfDataToBePassedIn;
#end
#interface yourBaseClass:UITableViewController
#property (nonatomic, weak) id<MyDelegate> myDelegate;
#end
In yourBaseClass.m
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
self.isScrolling = YES;
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
//[super scrollViewDidEndDragging:scrollView willDecelerate:decelerate]; // pull to refresh
if(!decelerate) {
self.isScrolling = NO;
if(self.myDelgate && [self.myDelegate respondsToSelector(callMethodThatRequiresTableViewAndArrayOfDataToBePassedIn)])
{
[self.myDelegate callMethodThatRequiresTableViewAndArrayOfDataToBePassedIn];
}
}
}
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
self.isScrolling = NO;
if(self.myDelgate && [self.myDelegate respondsToSelector(callMethodThatRequiresTableViewAndArrayOfDataToBePassedIn)])
{
[self.myDelegate callMethodThatRequiresTableViewAndArrayOfDataToBePassedIn];
}
}
- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView
{
self.isScrolling = NO;
}
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
{
self.isScrolling = NO;
}
Now you have to just implement the myDelegate method callMethodThatRequiresTableViewAndArrayOfDataToBePassedIn in your subclasses.
And yes also set the
self.myDelegate=self;
in your subclass viewDidLoad method.
With this approach you need not to pass any tableView or dataArray.
Hope this helps.