Ch. 4 -- Split-View Based App, pg. 121

sirab33 · May 24th, 2011, 10:10 PM

On pg. 121 there's an explanation section (a "How it Works") pertaining to the Split-View App that displays all those Denzel Washington movie posters. Well in the middle of pg. 121 it says:

"The 'tableView: cellForRowAtIndexPath:' method is fired for each item in the mutable array, thereby populating the Table view"

- I don't get it.
HOW is this method "fired" for "each item" in the array? I don't see a loop that's set to run 10 times - not here, not anywhere. I don't see where this method gets called otherwise in other parts of the program - what's the deal? How is this working?

Here's the code:

Code:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    static NSString *CellIdentifier = @"CellIdentifier";
    
    // Dequeue or create a cell of the appropriate type.
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault 
									   reuseIdentifier:CellIdentifier] autorelease];
        cell.accessoryType = UITableViewCellAccessoryNone;
    }
    
    // Configure the cell.
    //cell.textLabel.text = [NSString stringWithFormat:@"Row %d", indexPath.row];
	
	cell.textLabel.text =[listOfMovies objectAtIndex: indexPath.row];
    return cell;
}

thepianoguy · May 24th, 2011, 11:41 PM

The UITableView has built in functionality to draw itself.
The UITableViewDataSource Protocol methods are called by the tableView and provide information about size.

Required protocol methods as implemented in the project:

Code:

- (NSInteger)numberOfSectionsInTableView:(UITableView *)aTableView {
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)aTableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    //return 10;
	return[listOfMovies count];
}

The (numberOfSections * numberOfRows) informs the tableView how many times it will call

Code:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPathâ¦

which provides the information for each cell.
The tableView will automatically load the data when the view is displayed, updates are sometimes handled with -reloadData. Other updates such as insertion and deletion are handled differently. The documentation covers this.

Bob

sirab33 · May 25th, 2011, 06:37 PM

Got it!

Understood.

Thanks for the straight-forward explanation - much clearer than the Documentation, which I read but which only served to confuse me...

Much Obliged Sir