How to subclass CPTextField and customize behavior using becomeFirstResponder and assignFirstResponder

gistfile1.m

/*
 * AppController.j
 * NewApplication
 *
 * Created by You on May 21, 2009.
 * Copyright 2009, Your Company All rights reserved.
 */

@import <Foundation/CPObject.j>


@implementation AppController : CPObject
{
}

- (void)applicationDidFinishLaunching:(CPNotification)aNotification
{
    var theWindow = [[CPWindow alloc] initWithContentRect:CGRectMakeZero() styleMask:CPBorderlessBridgeWindowMask],
        contentView = [theWindow contentView];

    var label = [MyTextField textFieldWithStringValue:nil placeholder:@"PLACEHOLDER" width:300];

    [label setAutoresizingMask:CPViewMinXMargin | CPViewMaxXMargin | CPViewMinYMargin | CPViewMaxYMargin];
    [label setCenter:[contentView center]];

    [contentView addSubview:label];

    [theWindow orderFront:self];

    // Uncomment the following line to turn on the standard menu bar.
    //[CPMenu setMenuBarVisible:YES];
}

@end


// Custom subclass of CPTextField
@implementation MyTextField : CPTextField
{
}

- (BOOL)becomeFirstResponder
{
    [self setFont:[CPFont boldSystemFontOfSize:12.0]];
    [super becomeFirstResponder];
    return YES;
}

- (BOOL)resignFirstResponder
{
    [self setFont:[CPFont systemFontOfSize:12.0]];
    [super resignFirstResponder];
    return YES;
}

@end