ZGPullDragTableView/ZGPullDragTableViewClass/UITableView+ZGPullDrag.m

//
//  UITableView+ZGPullDrag.m
//  ZGPullDragTableView
//
//  Created by Kyle Fang on 2/26/13.
//  Copyright (c) 2013 Kyle Fang. All rights reserved.
//

#import "UITableView+ZGPullDrag.h"
#import <objc/runtime.h>

static char UITableViewZGPullViewDelegate;
static char UITableViewZGDragViewDelegate;
static char UITableViewZGPullDragViewObserving;
static char UITableViewZGPullView;
static char UITableViewZGDragView;

@interface UITableView (ZGPullDragPropertyCategory)
@property (nonatomic) BOOL isObserving;
@property (nonatomic, assign) UIView *pullView;
@property (nonatomic, assign) UIView *dragView;
@end

@implementation UITableView (ZGPullDragPropertyCategory)

- (void)setIsObserving:(BOOL)isObserving {
    if (self.isObserving == YES && isObserving == NO) {
        @try {
            [self removeObserver:self forKeyPath:@"contentOffset"];
        }
        @catch (NSException *exception) {
            //It's not observing
        }
    } else if (self.isObserving == NO && isObserving == YES) {
        [self addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew context:nil];
    }
    
    [self willChangeValueForKey:@"isObserving"];
    objc_setAssociatedObject(self, &UITableViewZGPullDragViewObserving,
                             [NSNumber numberWithBool:isObserving],
                             OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    [self didChangeValueForKey:@"isObserving"];
}

- (BOOL)isObserving {
    NSNumber *number = objc_getAssociatedObject(self, &UITableViewZGPullDragViewObserving);
    if (number == nil) {
        return NO;
    } else {
        return [number boolValue];
    }
}

- (void)setPullView:(UIView *)pullView{
    [self willChangeValueForKey:@"pullView"];
    objc_setAssociatedObject(self, &UITableViewZGPullView, pullView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    [self didChangeValueForKey:@"pullView"];
}

- (UIView *)pullView{
    return objc_getAssociatedObject(self, &UITableViewZGPullView);
}

- (void)setDragView:(UIView *)dragView{
    [self willChangeValueForKey:@"dragView"];
    objc_setAssociatedObject(self, &UITableViewZGDragView, dragView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    [self didChangeValueForKey:@"dragView"];
}

- (UIView *)dragView{
    return objc_getAssociatedObject(self, &UITableViewZGDragView);
}

@end

@implementation UITableView (ZGPullDrag)

@dynamic ZGDragViewDelegate, ZGPullViewDelegate;

- (void)setZGPullViewDelegate:(id<ZGPullViewDelegate>)ZGPullViewDelegate{
    [self willChangeValueForKey:@"ZGPullViewDelegate"];
    objc_setAssociatedObject(self, &UITableViewZGPullViewDelegate, ZGPullViewDelegate, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    [self didChangeValueForKey:@"ZGPullViewDelegate"];
}

- (id<ZGPullViewDelegate>)ZGPullViewDelegate{
    return objc_getAssociatedObject(self, &UITableViewZGPullViewDelegate);
}

- (void)setZGDragViewDelegate:(id<ZGDragViewDelegate>)ZGDragViewDelegate{
    [self willChangeValueForKey:@"ZGDragViewDelegate"];
    objc_setAssociatedObject(self, &UITableViewZGDragViewDelegate, ZGDragViewDelegate, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    [self didChangeValueForKey:@"ZGDragViewDelegate"];
}

- (id<ZGDragViewDelegate>)ZGDragViewDelegate{
    return objc_getAssociatedObject(self, &UITableViewZGDragViewDelegate);
}

- (void)addZGPullView:(UIView *)pullView{
    pullView.frame = CGRectOffset(pullView.frame, -pullView.frame.origin.x, -pullView.frame.origin.y-pullView.frame.size.height);
    [self addSubview:pullView];
    self.pullView = pullView;
    self.isObserving = YES;
}

- (void)addZGDragView:(UIView *)dragView{
    [self layoutIfNeeded];
    CGFloat originY = MAX(self.frame.size.height, self.contentSize.height);
    dragView.frame = CGRectOffset(dragView.frame, -dragView.frame.origin.x, -dragView.frame.origin.y+originY);
    [self addSubview:dragView];
    self.dragView = dragView;
    self.isObserving = YES;
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if ([keyPath isEqualToString:@"contentOffset"]) {
        [self scrollViewDidScroll:[[change valueForKey:NSKeyValueChangeNewKey] CGPointValue]];
    }
}

- (void)scrollViewDidScroll:(CGPoint )contentOffset {
    CGFloat yOffset = contentOffset.y;
    if (yOffset<0) {
        [self pullViewHandler:-yOffset];
    } else if (self.dragView.frame.origin.y == self.frame.size.height) {
        [self dragViewHandler:yOffset];
    } else if (self.dragView.frame.origin.y == self.contentSize.height && yOffset > self.dragView.frame.origin.y - self.frame.size.height) {
        [self dragViewHandler:yOffset-(self.dragView.frame.origin.y - self.frame.size.height)];
    }
}

- (void)pullViewHandler:(CGFloat )visiblePixels{
    if ([self.ZGPullViewDelegate respondsToSelector:@selector(pullView:Show:ofTotal:)]) {
        [self.ZGPullViewDelegate pullView:self.pullView Show:visiblePixels ofTotal:self.pullView.frame.size.height];
    }
    if (visiblePixels>self.pullView.frame.size.height && !self.isDragging) {
        [UIView animateWithDuration:0.1
                         animations:^{
                             self.contentInset = UIEdgeInsetsMake(self.pullView.frame.size.height, 0, 0, 0);
                         } completion:^(BOOL finished) {
                             if ([self.ZGPullViewDelegate respondsToSelector:@selector(pullView:hangForCompletionBlock:)]) {
                                 [self.ZGPullViewDelegate pullView:self.pullView hangForCompletionBlock:^{
                                     [[NSOperationQueue mainQueue] addOperationWithBlock:^{
                                         [UIView animateWithDuration:0.2 animations:^{
                                             self.contentInset = UIEdgeInsetsZero;
                                         }];
                                     }];
                                 }];
                             }
                         }];
    }
}


- (void)dragViewHandler:(CGFloat )visiblePixels{
    if ([self.ZGDragViewDelegate respondsToSelector:@selector(dragView:Show:ofTotal:)]) {
        [self.ZGDragViewDelegate dragView:self.dragView Show:visiblePixels ofTotal:self.dragView.frame.size.height];
    }
    if (visiblePixels>self.dragView.frame.size.height && !self.isDragging) {
        [UIView animateWithDuration:0.1
                         animations:^{
                             self.contentInset = UIEdgeInsetsMake(0, 0, self.dragView.frame.size.height, 0);
                         } completion:^(BOOL finished) {
                             if ([self.ZGDragViewDelegate respondsToSelector:@selector(dragView:hangForCompletionBlock:)]) {
                                 [self.ZGDragViewDelegate dragView:self.dragView hangForCompletionBlock:^{
                                     [[NSOperationQueue mainQueue] addOperationWithBlock:^{
                                         [UIView animateWithDuration:0.2 animations:^{
                                             self.contentInset = UIEdgeInsetsZero;
                                         }];
                                     }];
                                 }];
                             }
                         }];
    }
}

- (void)dealloc{
    if (self.isObserving) {
        self.isObserving = NO;
    }
}

@end