Beginner question - Cocoa outlet using a method
Beginner question - Cocoa outlet using a method
- Subject: Beginner question - Cocoa outlet using a method
- From: Denis Stanton <email@hidden>
- Date: Sun, 26 Jan 2003 14:29:56 +1300
I'm just starting with Cocoa. I've worked through some tutorial
examples and now I'm trying to branch out. I have written a very
simple extension to an example, but it doesn't work the way I expect.
Can someone tell me what I've missed?
The program displays a Table View. I'm trying to add a simple text
field to display the number of rows. I have a numberOfRowsInTableView
method so I thought it would be simple to connect this to a text field
set up in IB as follows:
-------- MyDataSource.h -----------
#import <Cocoa/Cocoa.h>
@interface MyDataSource : NSObject
{
IBOutlet NSTextField *numberOfRowsInTableView;
NSMutableArray *myArray; // initialization code not shown
}
@end
-------- MyDataSource.m --------
#import "MyDataSource.h"
@implementation MyDataSource
- (int)numberOfRowsInTableView:(NSTableView *)tableView {
return [myArray count];
}
@end
This does not work. The text field connected to the
numberOfRowsInTableView outlet in Interface builder never receives the
count of the array rows.
I have found that I can get around this by declaring an instance
variable for the IBOutlet and then explicitly assigning it a value
inside the numberOfRowsInTableView method.
-------- MyDataSource.h -----------
#import <Cocoa/Cocoa.h>
@interface MyDataSource : NSObject
{
IBOutlet NSTextField *myNumberOfRows;
NSMutableArray *myArray; // initialization code not shown
}
@end
-------- MyDataSource.m --------
#import "MyDataSource.h"
@implementation MyDataSource
- (int)numberOfRowsInTableView:(NSTableView *)tableView {
[myNumberOfRows setIntValue: [myArray count]];
return [myArray count];
}
This works, but it looks very clumsy to me. I would have thought that
the method that returns the rows could be connected directly to the
outlet rather than have to communicate through an extra variable.
Have I missed something basic?
Thank you for your time in reading so far
Denis
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