UISwitch with block handler

UIBlockSwitch.m

@interface UIBlockSwitch : UISwitch {
    ActionBlock _actionBlock;
}

-(void) handleControlEvent:(UIControlEvents)event
                 withBlock:(ActionBlock) action;

@end

@implementation UIBlockSwitch

-(void) handleControlEvent:(UIControlEvents)event
                 withBlock:(ActionBlock) action
{
    _actionBlock = action;
    [self addTarget:self action:@selector(callActionBlock:) forControlEvents:event];
}

-(void) callActionBlock:(id)sender{
    _actionBlock();
}

@end

Where is ActionBlock?