Blinking Label Operation

BlinkingColors.h

//
//  BlinkingColors.h

#import <Foundation/Foundation.h>

@interface BlinkingColors : NSObject {
@private 
    UIColor *back_;
    UIColor *text_;
}

@property (nonatomic, readonly) UIColor *backgroundColor;
@property (nonatomic, readonly) UIColor *textColor;

- (id)init;
- (id)initWithBackgroundColor:(UIColor *)back textColor:(UIColor *)text;

@end

BlinkingColors.m

//
//  BlinkingColors.m

#import "BlinkingColors.h"

@implementation BlinkingColors

@synthesize backgroundColor = back_;
@synthesize textColor = text_;

- (id)init {
    [self release];
    @throw [NSException exceptionWithName:NSInternalInconsistencyException
                                   reason:@"-init is not a valid initializer for the class BlinkingColors"
                                 userInfo:nil];
    return nil;
}

- (id)initWithBackgroundColor:(UIColor *)back textColor:(UIColor *)text {
    self = [super init];
    if (self) {
        back_ = [back retain];
        text_ = [text retain];
    }
    return self;
}

- (void)dealloc {
    [back_ release];
    [text_ release];
    [super dealloc];
}

@end

BlinkingLabelOperation.h

//
//  BlinkingLabelOperation.h

#import <Foundation/Foundation.h>

@class BlinkingColors;

@interface BlinkingLabelOperation : NSOperation {
@private
    BOOL mode_;
    UILabel *label_;
    NSTimeInterval interval_;
    
    BlinkingColors *blinkColors_;
    BlinkingColors *normalColors_;
}

- (id)init;
- (id)initWithLabel:(UILabel *)label freq:(NSTimeInterval)interval blinkColors:(BlinkingColors *)blink;
- (id)initWithLabel:(UILabel *)label freq:(NSTimeInterval)interval 
       normalColors:(BlinkingColors *)normal blinkColors:(BlinkingColors *)blink;

@end

BlinkingLabelOperation.m

//
//  BlinkingLabelOperation.m

#import "BlinkingLabelOperation.h"
#import "BlinkingColors.h"

@interface BlinkingLabelOperation ()
- (void)updateLabel;
@end

@implementation BlinkingLabelOperation

- (id)init {
    [self release];
    @throw [NSException exceptionWithName:NSInternalInconsistencyException
                                   reason:@"-init is not a valid initializer for the class BlinkingLabelOperation"
                                 userInfo:nil];
    return nil;
}

// default initializer
- (id)initWithLabel:(UILabel *)label freq:(NSTimeInterval)interval normalColors:(BlinkingColors *)normal blinkColors:(BlinkingColors *)blink {
    self = [super init];
    if (self) {
        mode_ = YES;
        interval_ = interval;
        normalColors_ = [normal retain];
        blinkColors_ = [blink retain];
        
        // Dont retain the label, because if the view unloads
        // the operation stop
        label_ = label;
    }
    return self;
}

- (id)initWithLabel:(UILabel *)label freq:(NSTimeInterval)interval blinkColors:(BlinkingColors *)blink {
    // get the current color of label as the normal color
    BlinkingColors *normal = [[BlinkingColors alloc] initWithBackgroundColor:label.backgroundColor
                                                                   textColor:label.textColor];
    // call the designated initializer
    return [self initWithLabel:label freq:interval
                  normalColors:normal blinkColors:blink];
}

- (void)main {
    SEL update = @selector(updateLabel);
    [self setThreadPriority:0.0];
    
    while (![self isCancelled]) {
        if (label_ == nil)
            break;
        
        [NSThread sleepForTimeInterval:interval_];
        [self performSelectorOnMainThread:update withObject:nil waitUntilDone:YES];
    }
}

- (void)updateLabel {
    BlinkingColors *currentColors = nil;
    
    if (mode_)
        currentColors = blinkColors_;
    else
        currentColors = normalColors_;
    
    [label_ setTextColor:currentColors.textColor];
    [label_ setBackgroundColor:currentColors.backgroundColor];

    mode_ = !mode_;
}

- (void)dealloc {
    [blinkColors_ release];
    [normalColors_ release];
    // don't release the label because I never owned it
    [super dealloc];
}

@end