Objective-C: Am I Properly Using this Delegate? - objective-c

Question

I have a mainWindowController that contains a tabView (which I'm using to switch between views on the main window).
I have view controllers (each with a nib file) for each view. One of the views, view A, contains a tableView. I need to use a delegate method to accomplish something.
After an hour or two or web research and reading up on delegates (new concept to me), I finally got my program to achieve the result I wanted it to for view A.
Here's the interface declaration for view A:
#interface ViewAController : NSViewController <NSTableViewDelegate>
- (BOOL) tableView:(NSTableView *)tableView shouldEditTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row;
As you can see, I'm using NSTableViewDelegate and I need to disable editing of table columns. The implementation looks like this for the method:
- (BOOL) tableView:(NSTableView *)tableView shouldEditTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row
{
NSLog(#"shouldEditTableColumn called");
return NO;
}
I used NSLog to make sure the function is being called.
Now in the SAME view controller (view A), I disable editing by clicking a button:
- (IBAction)turnOffEditing:(id)sender
{
[self.tableView setDelegate:self];
[self tableView:self.tableView shouldEditTableColumn:self.columnTableName row:0];
[self tableView:self.tableView shouldEditTableColumn:self.columnTableName row:1];
NSLog(#"turnOffEditing");
}
As you can see, I get the tableView from the view controller and assign the delegate to self.
I then call the shouldEditTableColumn method on self.
Now, everything works. However, is this the correct way to use a delegate? If I need to use more delegate methods for NSTableView for view A (the only view which will have a table), I'm assuming I can define them in View A's controllers as I did previously?

Answer 1

Usually, the delegate is the delegate from the start. That is, it's a bit strange to set the delegate in the -turnOffEditing: action method. Of course, for my suggestion to work, you'd want to return some dynamic value, like the value of a boolean flag instance variable, from the delegate method.
Also, you shouldn't be calling the delegate method yourself in the action method. That does nothing. The delegate is a thing which the frameworks call when they need to make a decision about how to behave.
So, I'd change your code to something like:
#property BOOL editingDisabled;
- (BOOL) tableView:(NSTableView *)tableView shouldEditTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row
{
NSLog(#"shouldEditTableColumn called");
return self.editingDisabled;
}
- (IBAction)turnOffEditing:(id)sender
{
self.editingDisabled = TRUE;
NSLog(#"turnOffEditing");
}
You'd want to set the delegate during setup. A good approach is to simply connect the table view's delegate outlet to your controller in the NIB.