Question

I have the following code:

@interface AXWindowController : NSWindowController {
IBOutlet NSTextField *text;
IBOutlet NSTextField *otherText;
}

- (void) setText: (NSString *)input;
- (void) setOtherText;

@end

@implementation AXWindowController

- (void) setText: (NSString *)input
{
    [text setStringValue:input];
}

- (void) setOtherText
{
    [otherText setStringValue:@"nag"];
}

@end

And when I run:

1. [controller showWindow:nil];
2. [controller setText:@"lol"];
3. [controller setOtherText];

Line 3 executes correctly, but line 2 does nothing. In fact, when I look at text and otherText in gdb while executing lines 2 and 3, I get the following results:

(gdb) p text
$1 = (NSTextField *) 0x0
(gdb) p otherText
$2 = (NSTextField *) 0x1385d1e0

What is happening? I can’t pass in the input variable to a set function for an NSTextField? Why is my NSTextField becoming null when I change the parameters of the set function?

Answer 1

It’s well known KVC issue.

When Cocoa loading your NIB to connect outlets connections designed in IB, it will look for setter.
So, it calls setText: with NSTextField* object while loading.
Since your code not ready to accept different kind of objects… first for configure outlet, second for set its internal text value… your outlet will stay equal to nil.

All calls to nil – does nothing.

Workaround: rename outlet variable name or rename setter/getter methods to be different from KVC notation…