BloodMagic

Provides kind of custom property attributes.

@interface ViewController : UIViewController
    <BMLazy>

@property (nonatomic, strong) ProgressViewService *progressViewService;
@property (nonatomic, strong) ResourceLoader *resourceLoader;

@end

@implementation ViewController

@dynamic progressViewService;
@dynamic resourceLoader;

- (void)loadResources
{
    [self.progressViewService showProgressInView:self.view];

    self.resourceLoader.delegate = self;
    [self.resourceLoader loadResources];
}

@end

progressViewService and resourceLoader will be initialized on demand.