CKSpinnerView - Emulating the app download spinner in the iOS 7 App Store

CKSpinnerView.h

//
//  CKSpinnerView.h
//
//  Created by Conrad Kramer on 9/19/13.
//  Copyright (c) 2013 Conrad Kramer. All rights reserved.
//

#import <CKShapeView/CKShapeView.h>

@interface CKSpinnerView : CKShapeView

@property (nonatomic, getter = isAnimating) BOOL animating;

@end

CKSpinnerView.m

//
//  CKSpinnerView.m
//
//  Created by Conrad Kramer on 9/19/13.
//  Copyright (c) 2013 Conrad Kramer. All rights reserved.
//

#import "CKSpinnerView.h"

static NSString * const CKSpinnerViewAnimationKey = @"spin";

@implementation CKSpinnerView

@dynamic animating;

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.animating = YES;
        self.strokeStart = 0.075f;
        self.lineWidth = 1;
        self.fillColor = nil;
        self.strokeColor = self.tintColor;
    }
    return self;
}

- (void)setAnimating:(BOOL)animating {
    if (animating) {
        CABasicAnimation *spin = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
        spin.fromValue = @0.0f;
        spin.toValue = @(2*M_PI);
        spin.duration = 1.0f;
        spin.repeatCount = HUGE_VALF;
        [self.layer addAnimation:spin forKey:CKSpinnerViewAnimationKey];
    } else {
        [self.layer removeAnimationForKey:CKSpinnerViewAnimationKey];
    }
}

- (BOOL)isAnimating {
    return ([self.layer animationForKey:CKSpinnerViewAnimationKey] != nil);
}

- (void)layoutSubviews {
    [super layoutSubviews];
    CGPoint center = CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds));
    self.path = [UIBezierPath bezierPathWithArcCenter:center radius:13 startAngle:0 endAngle:2*M_PI clockwise:YES];
}

- (void)tintColorDidChange {
    self.strokeColor = self.tintColor;
}

- (CGSize)intrinsicContentSize {
    return CGSizeMake(26, 26);
}

@end