参考链接：http://www.cocoachina.com/cms/wap.php?action=article&id=25786
//www.greatytc.com/p/2a6b41be045f
//www.greatytc.com/p/3517619085f7

一.IGList中的几个基本概念

Instagram在2016年年底发布了基于数据驱动的UICollectionView框架IGListKit。使用数据驱动去创造更为快速灵活的列表控件。以下是该框架的特点：

数据驱动（数据改变 -> Diff算法 -> update界面）
可重复单元和组件的更好体系结构
解耦的差异算法
可以为数据模型自定义差异算法
可扩展的API

IGListKit：一个数据驱动的UICollectionView框架，用于构建快速灵活的列表。
ListAdapter:
适配器，它将collectionview的dataSource和delegate统一了起来，负责collectionView数据的提供、UI的更新以及各种代理事件的回调。

ListSectionController:
一个 section controller是一个抽象UICollectionView的section的controller对象，指定一个数据对象，它负责配置和管理 CollectionView 中的一个 section 中的 cell。这个概念类似于一个用于配置一个 view 的 view-model：数据对象就是 view-model，而 cell 则是 view，section controller 则是二者之间的粘合剂。

二.实现
新建ViewController和一些SectionController（继承
IGListSectionController并遵守IGListSectionType）

在viewController中设置UI

    UICollectionViewFlowLayout *layout=[[UICollectionViewFlowLayout alloc]init];

    
    _collectionView=[[IGListCollectionView alloc]initWithFrame:CGRectZero collectionViewLayout:layout];
    
    IGListAdapterUpdater *updater=[[IGListAdapterUpdater alloc]init];

    _adapter=[[IGListAdapter alloc]initWithUpdater:updater viewController:self workingRangeSize:0];
    
    _adapter.collectionView=_collectionView;
    
    _adapter.delegate=self;
    _adapter.dataSource=self;
    
    [self.view addSubview:_collectionView];

绑定数据列表

- (NSArray<id <IGListDiffable>> *)objectsForListAdapter:(IGListAdapter *)listAdapter{
     
    return  (NSArray<id <IGListDiffable>> *)self.array;
}

绑定IGListSectionController

- (IGListSectionController <IGListSectionType> *)listAdapter:(IGListAdapter *)listAdapter sectionControllerForObject:(id)object{
//section初始化方法  ,此时可以传递数据过去
        
    A *a=[[A alloc]init];
    NSLog(@"%@",[object class]);
    if ([object isKindOfClass:[NSNumber class]]) {
        return [B new];
    }
    
    return (IGListSectionController <IGListSectionType> *)a;
}

//数据为空的时候返回一个view
- (nullable UIView *)emptyViewForListAdapter:(IGListAdapter *)listAdapter{
    UIView*view=[UIView new];
    view.backgroundColor=[UIColor blueColor];
    view.frame=CGRectMake(0, 50, 100, 100);

    return view ;
}

//将要显示secViewVC了.
- (void)listAdapter:(IGListAdapter *)listAdapter willDisplayObject:(id)object atIndex:(NSInteger)index{
     
}
//已经结束显示sectionVC了.
- (void)listAdapter:(IGListAdapter *)listAdapter didEndDisplayingObject:(id)object atIndex:(NSInteger)index{

}

三.代码

//
//  ViewController.h

#import <UIKit/UIKit.h>

#import <IGListKit.h>
#import "IGListDiffable.h"

@interface ViewController : UIViewController


@end

//
//  ViewController.m

#import "ViewController.h"

#import "A.h"
#import "B.h"
//#import "nn.h"

@interface ViewController ()<IGListAdapterDelegate,IGListAdapterDataSource>

@property (nonatomic , strong ) NSArray * array;

@property (nonatomic , assign ) int a ;

@end


@implementation ViewController{

    IGListCollectionView*_collectionView;
    IGListAdapter*_adapter;
}
-(NSArray*)array{
    if (_array==nil){
        
        _array=@[@"1",@"2",@"3",@"4",@5];
    }
    
    return _array;
    
    
    
}


-(void)viewWillAppear:(BOOL)animated{
    

}

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor=[UIColor whiteColor];
    
    UICollectionViewFlowLayout*layout=[[UICollectionViewFlowLayout alloc]init];

    
    _collectionView=[[IGListCollectionView alloc]initWithFrame:CGRectZero collectionViewLayout:layout];
    
    IGListAdapterUpdater*updater=[[IGListAdapterUpdater alloc]init];
    
    //layout和updater可以自己定义.
    
//    IGListAdapter*adapter=[[IGListAdapter alloc]initWithUpdater:updater viewController:self];
    _adapter=[[IGListAdapter alloc]initWithUpdater:updater viewController:self workingRangeSize:0];
    
    _adapter.collectionView=_collectionView;
    
    _adapter.delegate=self;
    _adapter.dataSource=self;
    
    [self.view addSubview:_collectionView];
    
    _collectionView.backgroundColor=[UIColor grayColor];
    
    _collectionView.alpha=0.5;
    
}

-(void)viewWillLayoutSubviews{
}

-(void)viewDidLayoutSubviews{

_collectionView.frame=self.view.bounds;
}

/**
 Asks the data source for the objects to display in the list.
 
 @param listAdapter The list adapter requesting this information.
 
 @return An array of objects for the list.
 */
//一一对应关系
- (NSArray<id <IGListDiffable>> *)objectsForListAdapter:(IGListAdapter *)listAdapter{

    return  (NSArray<id <IGListDiffable>> *)self.array;
    
}

/**
 Asks the data source for a section controller for the specified object in the list.
 
 @param listAdapter The list adapter requesting this information.
 @param object      An object in the list.
 
 @return A new section controller instance that can be displayed in the list.
 
 @note New section controllers should be initialized here for objects when asked. You may pass any other data to
 the section controller at this time.
 
 Section controllers are initialized for all objects whenever the `IGListAdapter` is created, updated, or reloaded.
 Section controllers are reused when objects are moved or updated. Maintaining the `-[IGListDiffable diffIdentifier]`
 guarentees this.
 */
- (IGListSectionController <IGListSectionType> *)listAdapter:(IGListAdapter *)listAdapter sectionControllerForObject:(id)object{
//section初始化方法  ,此时可以传递数据过去
    
    
    A*a=[[A alloc]init];
    NSLog(@"%@",[object class]);
    if ([object isKindOfClass:[NSNumber class]]) {
        return [B new];
    }
    
    return (IGListSectionController <IGListSectionType> *)a;
    
}

/**
 Asks the data source for a view to use as the collection view background when the list is empty.
 
 @param listAdapter The list adapter requesting this information.
 
 @return A view to use as the collection view background, or `nil` if you don't want a background view.
 
 @note This method is called every time the list adapter is updated. You are free to return new views every time,
 but for performance reasons you may want to retain the view and return it here. The infra is only responsible for
 adding the background view and maintaining its visibility.
 */
//数据为空的时候返回一个view
- (nullable UIView *)emptyViewForListAdapter:(IGListAdapter *)listAdapter{
    UIView*view=[UIView new];
    view.backgroundColor=[UIColor blueColor];
    view.frame=CGRectMake(0, 50, 100, 100);

    return view ;
}
//代理
/**
 Notifies the delegate that a list object is about to be displayed.
 
 @param listAdapter The list adapter sending this information.
 @param object      The object that will display.
 @param index       The index of the object in the list.
 */
//将要显示secViewVC了.
- (void)listAdapter:(IGListAdapter *)listAdapter willDisplayObject:(id)object atIndex:(NSInteger)index{

     
}

/**
 Notifies the delegate that a list object is no longer being displayed.
 
 @param listAdapter The list adapter sending this information.
 @param object      The object that ended display.
 @param index       The index of the object in the list.
 */
//已经结束显示sectionVC了.
- (void)listAdapter:(IGListAdapter *)listAdapter didEndDisplayingObject:(id)object atIndex:(NSInteger)index{

}
@end

//
//  A.h

#import <UIKit/UIKit.h>
#import <IGListKit.h>

@interface A : IGListSectionController<IGListSectionType>

@end

//
//  A.m

#import "A.h"

@interface A ()

@end

@implementation A{
    NSString*_object;

}

- (instancetype)init
{
    self = [super init];
    if (self) {
        self.inset=UIEdgeInsetsMake(2, 1, 2, 1);
        self.minimumLineSpacing=5;
        self.minimumInteritemSpacing=2;
        
        NSLog(@"我被创造出来了");      
        
    }
    return self;
}


- (NSInteger)numberOfItems{
    
    NSLog(@"%s",__func__);

   
    NSInteger a=2;
    
    NSLog(@"%f",self.collectionContext.containerSize.width);
    
     NSLog(@"返回数量%ld",a);
    return 20;
}


- (CGSize)sizeForItemAtIndex:(NSInteger)index{
     NSLog(@"返回大小");
    return  CGSizeMake(40, 80);
}

-(UICollectionViewCell *)cellForItemAtIndex:(NSInteger)index{

    UICollectionViewCell*cell=[self.collectionContext dequeueReusableCellOfClass:[UICollectionViewCell class] forSectionController:self atIndex:index];
        cell.backgroundColor=[UIColor redColor];
        
         NSLog(@"cell");
      
        return cell;
}

- (void)didUpdateToObject:(id)object{
  
    _object =[NSString stringWithFormat:@"%@",object];
    NSLog(@"%@",object);
}

- (void)didSelectItemAtIndex:(NSInteger)index{}


@end

//
//  B.h


#import <UIKit/UIKit.h>

#import <IGListKit.h>

@interface B : IGListSectionController<IGListSectionType>

@end

//
//  B.m

#import "B.h"

@interface B ()

@end

@implementation B{
    NSString*_object;
    
}



- (instancetype)init
{
    self = [super init];
    if (self) {
        self.inset=UIEdgeInsetsMake(2, 1, 2, 1);
        self.minimumLineSpacing=5;
        self.minimumInteritemSpacing=2;
        
        NSLog(@"我被创造出来了");
        
        
        
    }
    return self;
}



- (NSInteger)numberOfItems{
    
    NSLog(@"%s",__func__);
    
    
    NSInteger a=2;
    
    NSLog(@"%f",self.collectionContext.containerSize.width);
    
    NSLog(@"返回数量%ld",a);
    return 6;
}




- (CGSize)sizeForItemAtIndex:(NSInteger)index{
    
    NSLog(@"返回大小");
    return  CGSizeMake(40, 80);
    
}

-(UICollectionViewCell *)cellForItemAtIndex:(NSInteger)index{
    //    UICollectionViewCell*cell=[UICollectionViewCell new];
    //    collectionContext!.dequeueReusableCell(of: LabelCell.self, for: self, at: index) as! LabelCell
    UICollectionViewCell*cell=[self.collectionContext dequeueReusableCellOfClass:[UICollectionViewCell class] forSectionController:self atIndex:index];
    cell.backgroundColor=[UIColor orangeColor];
    
    
    NSLog(@"cell");
    
    
    return cell;
    
    
    
}

- (void)didUpdateToObject:(id)object{
    
    _object =[NSString stringWithFormat:@"%@",object];
    
    //    String(describing: object)
    NSLog(@"%@",object);
    
    
}

- (void)didSelectItemAtIndex:(NSInteger)index{}

@end