Example of a custom slider. You can copy the contents of C4WorkSpace, and then drag / drop the other two files into your project.

C4WorkSpace.m

//
//  Slider.h
//
//  Created by Travis Kirton.
//

#import "C4WorkSpace.h"
#import "Slider.h"

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

-(void)setup {
    CGPoint newCenter = self.canvas.center;
    newCenter.y -= 100;

    s1 = [[Slider alloc] initWithFrame:CGRectMake(0, 0, 500, 10)];
    [s1 rect:s1.frame];
    s1.center = newCenter;
    [self.canvas addShape:s1];
    [self listenFor:@"valueChanged" fromObject:s1 andRunMethod:@"updateSlider2"];

    newCenter.y += 100;

    s2 = [[Slider alloc] initWithFrame:CGRectMake(0, 0, 500, 10)];
    [s2 rect:s2.frame];
    s2.center = newCenter;
    [self.canvas addShape:s2];
    [self listenFor:@"valueChanged" fromObject:s2 andRunMethod:@"updateSlider1"];
}

-(void)updateSlider1 {
    s1.value = [C4Math tan:s2.value];
}

-(void)updateSlider2 {
    s2.value = [C4Math tan:s1.value];
}
@end

Slider.h

//
//  Slider.h
//
//  Created by Travis Kirton.
//

#import "C4Shape.h"

@interface Slider : C4Shape
@property (readwrite, nonatomic) CGFloat value;
@end

Slider.m

//
//  Slider.h
//
//  Created by Travis Kirton.
//

#import "Slider.h"

@implementation Slider {
    C4Shape *sliderButton;
    CGFloat minX, maxX;
    BOOL isSetup;
}

-(void)setup {
    if(!isSetup) {
        sliderButton = [C4Shape rect:CGRectMake(0, 0, 44, 44)];

        minX = sliderButton.center.x+(self.height-44)/2;
        maxX = self.width - minX;

        sliderButton.center = CGPointMake(minX ,self.height / 2.0);
        [self addShape:sliderButton];
        
        sliderButton.userInteractionEnabled = NO;
    }
    isSetup = YES;
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    CGPoint p = [[touches anyObject] locationInView:self];
    p.x = [C4Math constrain:p.x min:minX max:maxX];
    p.y = sliderButton.center.y;
    
    if(p.x != sliderButton.center.x) {
        sliderButton.center = p;
        _value = (sliderButton.center.x - minX)/(maxX - minX);
        [self postNotification:@"valueChanged"];
    }
}

-(void)setValue:(CGFloat)value {
    value = [C4Math constrainf:value min:0 max:1];
    if(_value != value) {
        _value = value;
        CGPoint newCenter = sliderButton.center;
        newCenter.x = _value * (maxX - minX) + minX;
        sliderButton.center = newCenter;
    }
}

@end