我习惯于用viewModel做数据层

好处：数据与VC层独立开来，结构清晰，方便处理；
缺点：一个VC对应一个viewModel

• 创建BaseViewModel基类

1. block作为回调

typedef void(^QYRequestCompletedBlock)(BOOL success,NSString *error,BOOL hasMoreData,BOOL isBlank);
success:请求成功与否；
error：错误提示；
hasMoreData：能否上拉加载更多；
isBlank：数据是否为空；

typedef void(^QYCacheCompletedBlock)(BOOL success,NSString *error);
success：数据是否为空；

2. 通用数据的定义

//vc直接读取dataArray
@property (nonatomic, strong) NSMutableArray *dataArray;

//true = 刷新； false ＝ 加载更多
@property (nonatomic, assign) BOOL refresh;

///分页
@property (nonatomic, assign) NSInteger pageIndex;
@property (nonatomic, assign) NSInteger pageSize;

3. 实现方法，改变的是pageIndex

- (void)loadLastestPage;//刷新pageIndex=0
- (void)loadNextPage;//加载下一页pageIndex++
//子类实现具体请求
- (void)loadItemsWithPageNum:(NSInteger)pageNum;

4. 缓存的读取

-(void)getCacheDataWithPath:(NSString*)fileName {
    NSArray *array = [QYFileManager readArrayWithFileName:fileName];
    
    [self.dataArray addObjectsFromArray:array];
    
    !self.cacheCompletedBlock ?: self.cacheCompletedBlock(self.dataArray.count>0,nil);
}

• 创建继承BaseViewModel的viewModel

具体的请求具体而论，可以添加筛选条件；

• 具体方法

- (void)loadItemsWithPageNum:(NSInteger)pageNum {
    [super loadItemsWithPageNum:pageNum];
    
    kWeakSelf(self);
    [[QYNetManager sharedInstance] loadDataWithParameters:@{@"method":@"info",@"short_conn":@(0)} path:@"api/v1/vpan" methodType:QYRequestType_POST success:^(id responseObject) {
        kStrongSelf(self);
        
        if (pageNum == 0) {
            self.dataArray = nil;//初始化、忽略缓存
        }
        //TODO:数据的处理
        BOOL hasMoreData = true;//是否数据加载完毕
        
        //data...
        
        if (pageNum == 0) {
            //第一页数据缓存
            
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),^{
                
                [QYFileManager saveArrayWithPath:self.dataArray fileName:@""];
            });
        }
        
        !self.requestCompletedBlock ?: self.requestCompletedBlock(true,nil,hasMoreData,self.dataArray.count>0);
    } failure:^(NSString *errorInfo) {
        kStrongSelf(self);
        
        !self.requestCompletedBlock ?: self.requestCompletedBlock(false,errorInfo,false,false);
    }];
    
}

• VC调用

一个get方法

- (ViewControllerViewModel *)viewModel {
    if (!_viewModel) {
        _viewModel = [[ViewControllerViewModel alloc] init];
        
        __block ViewControllerViewModel *temp_viewModel = _viewModel;
        kWeakSelf(self);
        _viewModel.requestCompletedBlock = ^(BOOL success,NSString *error,BOOL hasMoreData,BOOL isBlank) {
            kStrongSelf(self);
            
            [self.tableView.mj_header endRefreshing];
            [self.tableView.mj_footer endRefreshing];
            
            if (success) {
                
                if (!hasMoreData) {//是否有更多数据
                    [self.tableView.mj_footer endRefreshingWithNoMoreData];
                }
                
                if (isBlank) {
                    //数据为空
                    //TODO:添加缺省页面
                }else {
                    if (temp_viewModel.refresh) {
                        //下拉上拉刷新
                    }else {
                        //上拉刷新
                    }
                }
            }else {
                //TODO:给出错误提示
            }
        };
        
        _viewModel.cacheCompletedBlock = ^(BOOL success,NSString *error) {
            //缓存
        };
        
    }
    return _viewModel;
}

注意的是每次下拉刷新的时候手动设置viewModel的refresh为YES

Demo