touchesBegan (test example)

C4Workspace.m

//
//  C4WorkSpace.m
//  Examples
//
//  Created by Greg Debicki.
//

#import "C4WorkSpace.h"

@implementation C4WorkSpace {
    C4Shape *s1, *s2;
}

-(void)setup {
    [self setupShapes];
}

-(void) setupShapes {
    
    CGRect rect = CGRectMake(0, 0, 300, 75);
    
    s1 = [C4Shape rect:rect];
    s2 = [C4Shape rect:rect];
    
    CGPoint currentCenter = self.canvas.center;
    s1.center = currentCenter;
    s2.center = currentCenter;
    
    [self.canvas addShape:s1];
    [self.canvas addShape:s2];

    s1.animationDuration = 0.5f;
    s2.animationDuration = 0.5f;

}

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    
    CGPoint touchedPoint = [[touches anyObject] locationInView:self.view];
    
    
    
    if (touchedPoint.y <= self.canvas.height/2) {
        if (touchedPoint.x <= self.canvas.width/2){
            s2.rotation += PI/5.0f;
        }
        if (touchedPoint.x > self.canvas.width/2){
            s2.rotation -= PI/5.0f;
        }
    }
    if (touchedPoint.y > self.canvas.height/2) {
        if (touchedPoint.x <= self.canvas.width/2){
            s1.rotation += PI/5.0f;
        }
        if (touchedPoint.x > self.canvas.width/2){
            s1.rotation -= PI/5.0f;
        }
    }
    
}

@end

I would add this:

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    self.canvas.userInteractionEnabled = NO;

    CGPoint touchedPoint = [[touches anyObject] locationInView:self.view];

    if (touchedPoint.y <= self.canvas.height/2) {
        if (touchedPoint.x <= self.canvas.width/2){
            s2.rotation += PI/5.0f;
        }
        if (touchedPoint.x > self.canvas.width/2){
            s2.rotation -= PI/5.0f;
        }
        [self runMethod:@"allowInteraction" afterDelay:s2.animationDuration];
    }
    else if (touchedPoint.y > self.canvas.height/2) {
        if (touchedPoint.x <= self.canvas.width/2){
            s1.rotation += PI/5.0f;
        }
        if (touchedPoint.x > self.canvas.width/2){
            s1.rotation -= PI/5.0f;
        }
        [self runMethod:@"allowInteraction" afterDelay:s1.animationDuration];
    }

}

-(void)allowInteraction {
    self.canvas.userInteractionEnabled = YES;
}

... it shuts off user interaction for the duration of the animation.