How forward all methods from a delegate? - ios

Question

I'm subclassing UITableView and its protocol UITableViewDelegate and its "datasource" UITableDataSource, everything works fine but I haven't find the clean way to forward the methods from "delegate" and "datasource" from UITableView.
I have tried to "play" with respondsToSelector:, forwardingTargetForSelector: and forwardInvocation: methods of NSObject but I didn't get anything.
I'll show you some code about I'm trying:
My CustomTableView.h:
#protocol TableViewCustomDelegate <UITableViewDelegate>
- (void) anyCustomMethodDelegate;
#end
#protocol TableViewCustomDataSource <UITableViewDataSource>
- (NSInteger) anyCustomMethod;
#end
#interface TableViewCustom : UITableView <UITableViewDelegate, UITableViewDataSource>
#property (nonatomic, weak) id<TableViewCustomDelegate> myDelegate;
#property (nonatomic, weak) id<TableViewCustomDataSource> myDataSource;
#end
And this is my TableViewCustom.m:
#implementation TableViewCustom
-(BOOL)respondsToSelector:(SEL)aSelector {
if ([self.myDelegate respondsToSelector:aSelector]) {
return YES;
}
return [super respondsToSelector:aSelector];
}
-(id)forwardingTargetForSelector:(SEL)aSelector {
if ([self.myDelegate respondsToSelector:aSelector]) {
return self.myDelegate;
}
return [super forwardingTargetForSelector:aSelector];
}
...
...
- (void) setMyDelegate:(id<TableViewCustomDelegate>)delegate
{
[super setDelegate:self];
_myDelegate = delegate;
}
- (void) setMyDataSource:(id<TableViewCustomDataSource>)dataSource
{
[super setDataSource:self];
_myDataSource = dataSource;
}
..
..
// A method from UITableViewDelegate that I would like to avoid
-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
if ([self.delegateDelegate
respondsToSelector:#selector(tableView:viewForHeaderInSection:)]) {
return [self.myDelegate tableView:tableView
viewForHeaderInSection:section];
}
return nil;
}
..
..
#end
I would like to avoid conforms methods just to forward it to "myDelegate".
I think it should be work with responsToSelector: and forwardingTargetForSelector: like I do in my code but it doesn't work. I don't know if I'm doing something wrong or if it is not possible.
Thanks in advance.
Regards.

Answer 1

I might be misunderstanding your intent, but if you just want your subclass to utilize the standard delegate and datasource, just leave those methods alone and hand the subclass whatever delegate/datasource you want. e.g.
MyTableViewSubclass *tableView = [[MyTableViewSubclass alloc] initWithFrame:....];
tableView.datasource = // anything that implements UITableViewDatasource
tableView.delegate = // anything that implements UITableViewDelegate
Then don't do anything special with those properties or protocols in your subclass.

Answer 2

In order to make messaging work, you need to implement following methods:
-(void)forwardInvocation:(NSInvocation *)invocation {
SEL aSelector = [invocation selector];
if ([self.myDelegate respondsToSelector:aSelector]) {
[invocation invokeWithTarget:self.myDelegate];
}
}
-(NSMethodSignature*)methodSignatureForSelector:(SEL)selector {
NSMethodSignature *signature = [super methodSignatureForSelector:selector];
if (nil == signature) {
signature = [self.myDelegate methodSignatureForSelector:selector];
}
return signature;
}

Answer 3

Please see the comments lines for explanation
- (void) setMyDelegate:(id<TableViewCustomDelegate>)delegate
{
//you told you will handle delegate methods to SUPER in our case UITableView
[super setDelegate:self];
_myDelegate = delegate; //You have internally stored the delegate
}
In View For Header
//You are overriding this method
//Table View will not handle this as you have overridden.
-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
//You check whether your delegate can do that.
if ([self.delegateDelegate respondsToSelector:#selector(tableView:viewForHeaderInSection:)])
{
return [self.myDelegate tableView:tableView
viewForHeaderInSection:section];
}
//If you delegate is not doing, you need to handle that
// However returning nil. So Instead of UIView the framework gets nil
//You need to handle this if your delegate is not handling this
return nil;
}