I am in the process of writing my own gridview implementation( Based of the tableview pattern). I have followed a datasource model similar to table view, but when I check if the data source responds to the message the call always fails.

I have tried putting in break points and following execution, I even tried missing out the call to respondsToSelector. Nothing I try seems to work. What am I missing here? Thanks in advance

**GridView.h**

```
    ...
    @protocol GridViewDataSource 
    - (NSInteger) numberOfRowsForGridView:(GridView *)gridView;
    - (NSInteger) numberOfColumnsForGridView:(GridView *)gridView;

    - (GridViewCell *) cellForRow:(NSInteger) row column:(NSInteger )column;
    @end 

```

**GridView.m**

```
    ...
    #pragma mark datasource methods
    -(NSInteger)numberOfRowsForGridView
    {
        if( [dataSource respondsToSelector:@selector(numberOfRowsForGridView:)] )
           return [dataSource numberOfRowsForGridView:self];
       // NSLog(@"Failed, dataSource does not implement properly");
        return 0;
    }

    -(NSInteger)numberOfColumnsForGridView
    {
        if( [dataSource respondsToSelector:@selector(numberOfColumnsForGridView:)] )
            return [dataSource numberOfColumnsForGridView:self];
        return 0;
    }

    -(GridViewCell *)cellForRow:(NSInteger)row column:(NSInteger)column
    {
        if( [dataSource respondsToSelector:@selector(cellForRow:column:)])
            return [dataSource cellForRow:row column:column];
        return nil;
    }

```

**GridViewAppDelegate.h**

```
    ...
    @interface GridViewAppDelegate : NSObject <UIApplicationDelegate, GridViewDataSource>
    ...

```

**GridViewAppDelegate.m**

```
    #pragma mark datasource methods
    -(NSInteger)numberOfRowsForGridView:(GridView *)gridView
    {
        return 1;
    }

    -(NSInteger)numberOfColumnsForGridView:(GridView *)gridView
    {
        return 1;
    }

    -(GridViewCell *)cellForRow:(NSInteger)row column:(NSInteger)column
    {
        CGRect frame = [view bounds];

        GridViewCell *cell = [[GridViewCell alloc]initWithFrame:frame];
        return cell;
    }

```
['https://Stackoverflow.com/questions/7026438', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/299450/']
Is your `dataSource` object `nil`?

Any message sent to `nil` will return `NO` for boolean results *(0 for numbers, and `nil` for objects as well)*.
Have you checked whether `dataSource` is non-nil?