基本原理就是利用section的和row的关系，当点击section的头部view时候，就刷新下列表，展开当前section下的row，效果图如下：

折叠.gif

• 关键代码

//
//  ViewController.m
//  TableView的折叠收起
//
//  Created by liyang on 16/6/15.
//  Copyright © 2016年 liyang. All rights reserved.
//

#import "ViewController.h"

#import "LYTableViewCell.h"
#import "LYHeaderView.h"

#import "LYSectionItem.h"
#import "LYCellItem.h"

static NSString *const cellIdentifier = @"frinedCell";

@interface ViewController ()<UITableViewDelegate, UITableViewDataSource, HeaderViewDelegate>
@property(nonatomic, strong) UITableView *tableView;
@property (nonatomic, strong) NSArray *dataArray;
@end

@implementation ViewController

- (UITableView *)tableView
{
    if (!_tableView) {
        UITableView *tableView = [[UITableView alloc] init];
        tableView.frame = self.view.bounds;
        tableView.dataSource = self;
        tableView.delegate = self;
        tableView.backgroundColor = [UIColor clearColor];
        tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
        tableView.contentInset = UIEdgeInsetsMake(64, 0, 0, 0);
        tableView.scrollIndicatorInsets = UIEdgeInsetsMake(64, 0, 0, 0);
        [self.view addSubview:tableView];
        self.tableView = tableView;
    }
    return _tableView;
}

// 懒加载
- (NSArray *)dataArray
{
    if (!_dataArray) {
        
        NSArray *arr = @[ @{
                           @"sectionName":@"sectionName1",
                           @"cellItems":@[
                                   @{@"cellItemName":@"cellName1"},
                                   @{@"cellItemName":@"cellName2"},
                                   @{@"cellItemName":@"cellName3"}
                                   ]
                           },
                        @{
                          @"sectionName":@"sectionName2",
                          @"cellItems"  :@[
                                  @{@"cellItemName":@"cellName1"},
                                  @{@"cellItemName":@"cellName2"},
                                  @{@"cellItemName":@"cellName3"}
                                  ]
                          },
                        @{
                          @"sectionName":@"sectionName3",
                          @"cellItems":@[
                                  @{@"cellItemName":@"cellName1"},
                                  @{@"cellItemName":@"cellName2"},
                                  @{@"cellItemName":@"cellName3"}
                                  ]
                          }];
        NSMutableArray *tempArr = [NSMutableArray array];
        for (int i = 0; i < 6; i++) {
            for (NSDictionary *dic in arr) {
                LYSectionItem *model = [LYSectionItem sectionItemWithDic:dic];
                [tempArr addObject:model];
            }
        }
        self.dataArray = tempArr;
        
        [self.tableView reloadData];
    }
    return _dataArray;
}

- (void)viewDidLoad {
    [super viewDidLoad];
     [self.tableView registerClass:[LYTableViewCell class] forCellReuseIdentifier:cellIdentifier];
    [self dataArray];
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return self.dataArray.count;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    LYSectionItem *sectionItem = self.dataArray[section];
    // 条件表达式。得出row行数
    return sectionItem.isOpen ? sectionItem.cellItems.count : 0;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    LYTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];
    LYSectionItem *sectionItem = self.dataArray[indexPath.section];
    LYCellItem *cellItem = sectionItem.cellItems[indexPath.row];
    
    cell.cellItem = cellItem;
    
    return cell;
}

#pragma mark - UITableViewDelegate
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 50;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    LYSectionItem *sectionItem = self.dataArray[indexPath.section];
    LYCellItem *cellItem = sectionItem.cellItems[indexPath.row];
    return cellItem.cellHeight;
}
- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
    LYSectionItem *sectionItem = self.dataArray[section];
    LYHeaderView *header = [LYHeaderView headerView:tableView];
    header.delegate = self;
    header.sectionItem = sectionItem;
    return header;
}

- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
{
    return 40;
}
#pragma mark - HeaderViewDelegate
- (void)headerViewClick:(LYHeaderView *)headerView
{
    // 改变了isopen的值
    [self.tableView reloadData];//刷新列表
}

@end

• 自定义了一个TableView的头视图，当点击它的时候，通过控制模型isOpen属性来达到控制列表是否展开

//
//  LYHeaderView.m
//  TableView的折叠收起
//
//  Created by liyang on 16/6/15.
//  Copyright © 2016年 liyang. All rights reserved.
//

#import "LYHeaderView.h"
#import "LYSectionItem.h"

@interface LYHeaderView ()
@property (nonatomic, strong) UIButton *arrowBtn;
@property (nonatomic, strong) UILabel *titleLabel;
@end

@implementation LYHeaderView

+ (instancetype)headerView:(UITableView *)tableView
{
    static NSString *kHeadIdentifier = @"header";
    LYHeaderView *headerView = [tableView dequeueReusableHeaderFooterViewWithIdentifier:kHeadIdentifier];
    if (!headerView) {
        headerView = [[self alloc] initWithReuseIdentifier:kHeadIdentifier];
    }
    return headerView;
}

- (UIButton *)arrowBtn
{
    if (!_arrowBtn) {
        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
        [button setImage:[UIImage imageNamed:@"buddy_header_arrow"] forState:UIControlStateNormal];
        [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        // 距离
        button.contentEdgeInsets = UIEdgeInsetsMake(0, 10, 0, 0);
        //内容的水平对齐方式
        button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;
        button.titleEdgeInsets = UIEdgeInsetsMake(0, 10, 0, 0);
        button.imageView.contentMode = UIViewContentModeCenter;
        [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
        //不裁剪图片
        button.imageView.clipsToBounds = NO;
        [self addSubview:button];
        self.arrowBtn = button;
    }
    return _arrowBtn;
}
- (UILabel *)titleLabel
{
    if (!_titleLabel) {
        UILabel *labelRight = [[UILabel alloc] init];
        labelRight.textAlignment = NSTextAlignmentCenter;
        [self addSubview:labelRight];
        self.titleLabel = labelRight;
    }
    return _titleLabel;
}

- (void)setSectionItem:(LYSectionItem *)sectionItem
{
    _sectionItem = sectionItem;
    
    [self.arrowBtn setTitle:sectionItem.name forState:UIControlStateNormal];
    self.titleLabel.text = [NSString stringWithFormat:@"%ld", sectionItem.cellItems.count];
    
    // 添加观察者，观察isOpen属性的变化，来调节指示器的状态
    [self addObserver:self forKeyPath:@"sectionItem.isOpen" options:NSKeyValueObservingOptionInitial context:nil];
}

- (void)addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:(void *)context
{
    // 改变button图片的旋转读
    self.arrowBtn.imageView.transform = self.sectionItem.isOpen ? CGAffineTransformMakeRotation(M_PI_2) : CGAffineTransformMakeRotation(0);
}

//布局
- (void)layoutSubviews {
    [super layoutSubviews];
    self.arrowBtn.frame = self.bounds;
    self.titleLabel.frame = CGRectMake(self.bounds.size.width - 70, 0, 60, self.frame.size.height);
}

#pragma mark - buttonAction
- (void)buttonAction:(UIButton *)sender {
    //修改groupModel的isOpen属性
    self.sectionItem.isOpen = !self.sectionItem.isOpen;
    if ([self.delegate respondsToSelector:@selector(headerViewClick:)]) {
        [self.delegate headerViewClick:self];
    }
}
@end

• 主要就是练习模型控制View

[GitHub地址][1]
[1]:https://github.com/liyang123/TableView-.git