Example of tying the movement of two objects together with Listeners and Gestures

C4WorkSpace.m

//
//  C4WorkSpace.m
//
//  Created by Travis Kirton
//

#import "C4WorkSpace.h"

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

-(void)setup {
    s1 = [C4Shape ellipse:CGRectMake(0, 0, 44, 44)];
    s2 = [C4Shape ellipse:s1.frame];
    
    [self.canvas addShape:s2];
    [self.canvas addShape:s1];
    
    [s1 addGesture:PAN name:@"pan" action:@"move:"];
    [self listenFor:@"moved" fromObject:s1 andRunMethod:@"moveS2"];

    [s2 addGesture:PAN name:@"pan" action:@"move:"];
    [self listenFor:@"moved" fromObject:s2 andRunMethod:@"moveS1"];
}

-(void)moveS1 {
    CGPoint p = s2.center;
    p.x = s1.center.x;
    s1.center = p;
}

-(void)moveS2 {
    CGPoint p = s1.center;
    p.x = s2.center.x;
    s2.center = p;
}

@end