Simple, arbitrary, random, arc, diagrams.

C4WorkSpace.m

//
//  C4WorkSpace.m
//  arcDiagrams
//
//  Created by moi on 12-09-30.
//  Copyright (c) 2012 moi. All rights reserved.
//

#import "C4WorkSpace.h"

@implementation C4WorkSpace {
    C4Shape *arc1;
    CGPoint pts[2];
    BOOL canAddArc;
}

-(void)setup {
    canAddArc = YES;
}

-(void)touchesBegan {
    if(canAddArc) {
        canAddArc = NO;
        int i = [self.canvas.subviews count];
        if(i == 0) pts[0] = CGPointMake((CGFloat)[C4Math randomInt:(int)self.canvas.width],self.canvas.center.y);
        else pts[0] = pts[1];
        pts[1] = CGPointMake((CGFloat)[C4Math randomInt:(int)self.canvas.width], self.canvas.center.y);
        
        BOOL up = (i % 2 == 0) ? YES : NO;
        
        C4Shape *arc = [self arcBetweenPoints:pts up:up];
        arc.userInteractionEnabled = NO;
        
        [self.canvas addShape:arc];
        [self runMethod:@"animateArc:" withObject:arc afterDelay:0.05f];
    }
}

-(C4Shape *)arcBetweenPoints:(CGPoint *)beginEndPoints up:(BOOL)up {
    CGPoint p1 = beginEndPoints[0];
    CGPoint p2 = beginEndPoints[1];
    
    CGFloat radius = [C4Math absf:p2.x - p1.x]/2;
    
    CGPoint center = self.canvas.center;
    if(p2.x > p1.x) {
        center.x = p1.x + radius;
    } else {
        center.x = p2.x+radius;
    }
    
    CGFloat startAngle;
    if(up == YES) startAngle = PI;
    else startAngle = 0;
    
    CGFloat endAngle = startAngle + PI;
    
    C4Shape *s = [C4Shape arcWithCenter:center radius:radius
                             startAngle:startAngle endAngle:endAngle clockwise:YES];
    
    s.fillColor = [UIColor clearColor];
    
    if(p2.x > p1.x) {
        if(up) {
            s.strokeEnd = 0.0f;
        } else {
            s.strokeStart = 1.0f;
        }
    } else {
        if(up) {
            s.strokeStart = 1.0f;
        } else {
            s.strokeEnd = 0.0f;
        }
    }

    if(up) s.strokeColor = C4GREY;
    
    return s;
}

-(void)animateArc:(C4Shape *)arc {
    arc.animationDuration = 1.0f;
    if(arc.strokeStart == 1.0f) arc.strokeStart = 0.0f;
    else arc.strokeEnd = 1.0f;
    [self runMethod:@"canAdd" afterDelay:arc.animationDuration];
}

-(void)canAdd {
    canAddArc = YES;
}

@end