Runtime-Code-AssociatedObject

///-----------------------------------------------------------------------------
/// Associated Objects
/// http://nshipster.com/associated-objects
///-----------------------------------------------------------------------------

/**
 Associated Objects—or Associative References, as they were originally known—are a feature of the Objective-C 2.0 runtime, introduced in OS X Snow Leopard (available in iOS 4). The term refers to the following three C functions declared in , which allow objects to associate arbitrary values for keys at runtime:

 objc_setAssociatedObject
 objc_getAssociatedObject
 objc_removeAssociatedObjects
 Why is this useful? It allows developers to add custom properties to existing classes in categories, which is an otherwise notable shortcoming for Objective-C.

 http://nshipster.com/associated-objects
 */
@interface NSObject (AssociatedObject)
@property (nonatomic, strong) id associatedObject;
@end


@implementation NSObject (AssociatedObject)
@dynamic associatedObject;

/**
 It is often recommended that they key be a static char—or better yet, the
 pointer to one. Basically, an arbitrary value that is guaranteed to be constant,
 unique, and scoped for use within getters and setters:

 static char kAssociatedObjectKey;

 objc_getAssociatedObject(self, &kAssociatedObjectKey);

 http://nshipster.com/associated-objects
 */
- (void)setAssociatedObject:(id)object {
    objc_setAssociatedObject(self, @selector(associatedObject), object, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (id)associatedObject {
    return objc_getAssociatedObject(self, @selector(associatedObject));
}

@end

///-----------------------------------------------------------------------------
/// https://github.com/ltebean/LTNavigationBar
///-----------------------------------------------------------------------------
@implementation UINavigationBar (Awesome)

static char overlayKey;

- (UIView *)overlay
{
    return objc_getAssociatedObject(self, &overlayKey);
}

- (void)setOverlay:(UIView *)overlay
{
    objc_setAssociatedObject(self, &overlayKey, overlay, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (void)lt_setBackgroundColor:(UIColor *)backgroundColor
{
    if (!self.overlay) {
        [self setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
        self.overlay = [[UIView alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.bounds), CGRectGetHeight(self.bounds) + 20)];
        self.overlay.userInteractionEnabled = NO;
        self.overlay.autoresizingMask = UIViewAutoresizingFlexibleWidth;    // Should not set `UIViewAutoresizingFlexibleHeight`
        [[self.subviews firstObject] insertSubview:self.overlay atIndex:0];
    }
    self.overlay.backgroundColor = backgroundColor;
}

@end

///-----------------------------------------------------------------------------
/// https://github.com/forkingdog/FDFullscreenPopGesture
///-----------------------------------------------------------------------------
@interface UINavigationController (FDFullscreenPopGesture)

@property (nonatomic, strong, readonly) UIPanGestureRecognizer *fd_fullscreenPopGestureRecognizer;

@property (nonatomic, assign) BOOL fd_viewControllerBasedNavigationBarAppearanceEnabled;

@end

@implementation UINavigationController (FDFullscreenPopGesture)

- (UIPanGestureRecognizer *)fd_fullscreenPopGestureRecognizer
{
    UIPanGestureRecognizer *panGestureRecognizer = objc_getAssociatedObject(self, _cmd);

    if (!panGestureRecognizer) {
        panGestureRecognizer = [[UIPanGestureRecognizer alloc] init];
        panGestureRecognizer.maximumNumberOfTouches = 1;

        objc_setAssociatedObject(self, _cmd, panGestureRecognizer, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    return panGestureRecognizer;
}

- (BOOL)fd_viewControllerBasedNavigationBarAppearanceEnabled
{
    NSNumber *number = objc_getAssociatedObject(self, _cmd);
    if (number) {
        return number.boolValue;
    }
    self.fd_viewControllerBasedNavigationBarAppearanceEnabled = YES;
    return YES;
}

- (void)setFd_viewControllerBasedNavigationBarAppearanceEnabled:(BOOL)enabled
{
    SEL key = @selector(fd_viewControllerBasedNavigationBarAppearanceEnabled);
    objc_setAssociatedObject(self, key, @(enabled), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

@end

///-----------------------------------------------------------------------------
/// https://github.com/forkingdog/FDFullscreenPopGesture
///-----------------------------------------------------------------------------
@interface UIViewController (FDFullscreenPopGesture)

@property (nonatomic, assign) BOOL fd_interactivePopDisabled;

@property (nonatomic, assign) BOOL fd_prefersNavigationBarHidden;

@property (nonatomic, assign) CGFloat fd_interactivePopMaxAllowedInitialDistanceToLeftEdge;

@end

@implementation UIViewController (FDFullscreenPopGesture)

- (BOOL)fd_interactivePopDisabled
{
    return [objc_getAssociatedObject(self, _cmd) boolValue];
}

- (void)setFd_interactivePopDisabled:(BOOL)disabled
{
    objc_setAssociatedObject(self, @selector(fd_interactivePopDisabled), @(disabled), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (BOOL)fd_prefersNavigationBarHidden
{
    return [objc_getAssociatedObject(self, _cmd) boolValue];
}

- (void)setFd_prefersNavigationBarHidden:(BOOL)hidden
{
    objc_setAssociatedObject(self, @selector(fd_prefersNavigationBarHidden), @(hidden), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}


- (CGFloat)fd_interactivePopMaxAllowedInitialDistanceToLeftEdge
{
#if CGFLOAT_IS_DOUBLE
    return [objc_getAssociatedObject(self, _cmd) doubleValue];
#else
    return [objc_getAssociatedObject(self, _cmd) floatValue];
#endif
}

- (void)setFd_interactivePopMaxAllowedInitialDistanceToLeftEdge:(CGFloat)distance
{
    SEL key = @selector(fd_interactivePopMaxAllowedInitialDistanceToLeftEdge);
    objc_setAssociatedObject(self, key, @(MAX(0, distance)), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

@end

///-----------------------------------------------------------------------------
/// http://www.cnblogs.com/tangbinblog/p/3944316.html
/// category使用 objc_setAssociatedObject/objc_getAssociatedObject 实现添加属性
///-----------------------------------------------------------------------------

@interface NSObject (CategoryWithProperty)

@property (nonatomic, strong) NSObject *property;

@end

@implementation NSObject (CategoryWithProperty)

- (NSObject *)property {
    return objc_getAssociatedObject(self, @selector(property));
}

- (void)setProperty:(NSObject *)value {
    objc_setAssociatedObject(self, @selector(property), value, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

@end