How to fix Implementation error? - ios

Question

I have a error but the app runs fine its a page control that uses 3 view controllers in one UIscroll. The error reads \"Method definition for 'changePage:' not found" <---#implementation PagerViewController \ how can i fix this?
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#import "PagerViewController.h"
#interface PagerViewController ()
#property (assign) BOOL pageControlUsed;
#property (assign) NSUInteger page;
#property (assign) BOOL rotating;
- (void)loadScrollViewWithPage:(int)page;
#end
#implementation PagerViewController
#synthesize scrollView;
#synthesize pageControl;
#synthesize pageControlUsed = _pageControlUsed;
#synthesize page = _page;
#synthesize rotating = _rotating;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[self.scrollView setPagingEnabled:YES];
[self.scrollView setScrollEnabled:YES];
[self.scrollView setShowsHorizontalScrollIndicator:NO];
[self.scrollView setShowsVerticalScrollIndicator:NO];
[self.scrollView setDelegate:self];
}
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
for (NSUInteger i =0; i < [self.childViewControllers count]; i++) {
[self loadScrollViewWithPage:i];
}
self.pageControl.currentPage = 0;
_page = 0;
[self.pageControl setNumberOfPages:[self.childViewControllers count]];
UIViewController *viewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage];
if (viewController.view.superview != nil) {
[viewController viewWillAppear:animated];
}
self.scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * [self.childViewControllers count], scrollView.frame.size.height);
}
- (void)loadScrollViewWithPage:(int)page {
if (page < 0)
return;
if (page >= [self.childViewControllers count])
return;
// replace the placeholder if necessary
UIViewController *controller = [self.childViewControllers objectAtIndex:page];
if (controller == nil) {
return;
}
// add the controller's view to the scroll view
if (controller.view.superview == nil) {
CGRect frame = self.scrollView.frame;
frame.origin.x = frame.size.width * page;
frame.origin.y = 0;
controller.view.frame = frame;
[self.scrollView addSubview:controller.view];
}
}
// At the begin of scroll dragging, reset the boolean used when scrolls originate from the UIPageControl
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
_pageControlUsed = NO;
}
// At the end of scroll animation, reset the boolean used when scrolls originate from the UIPageControl
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
_pageControlUsed = NO;
}
#end
The error statement is "Method definition for 'changePage:; not found"
How do i fix this ?

Answer 1

That error (really a warning, not an error) is telling you that your #interface for that class says that the class objects should respond to the selector changePage: (either through direct definition or inheritance/delegation) but your #implementation section for the class does not have that selector defined anywhere.
This is a warning because it does not stop the compile, but it is possible that somewhere where you imported the .h file you call the function changePage: on an instance of that class. That will crash your app as it tries to find that function definition somewhere but can't.
The way to resolve this warning is to define the function changePage: somewhere in your #implementation for that class.