有時候我們的控制器會非常龐大，一部分原因就是控制器要獲取數據，可能包含從網絡中加載數據，這時候我們需要把獲取dataSource這部分代碼分離出來，創建一個新的類。

1. tableView分離dataSource

分離UITableViewController中的dataSource到一個單獨的類，并實現UITableViewDataSource協議及其方法。

ArrayDataSource.h

    typedef void (^TableViewCellConfigureBlock)(id cell, id item);

    @interface ArrayDataSource : NSObject <UITableViewDataSource>

    - (id)initWithItems:(NSArray *)anItems
         cellIdentifier:(NSString *)aCellIdentifier
         configureCellBlock:(TableViewCellConfigureBlock)aConfigureCellBlock;

    - (id)itemAtIndexPath:(NSIndexPath *)indexPath;

    @end           

ArrayDataSource.m

    @interface ArrayDataSource ()

    @property (nonatomic, strong) NSArray *items;
    @property (nonatomic, copy) NSString *cellIdentifier;
    @property (nonatomic, copy) TableViewCellConfigureBlock configureCellBlock;

    @end

    @implementation ArrayDataSource

    - (id)init
    {
        return nil;
    }

    - (id)initWithItems:(NSArray *)anItems
         cellIdentifier:(NSString *)aCellIdentifier
         configureCellBlock:(TableViewCellConfigureBlock)aConfigureCellBlock
    {
        self = [super init];
        if (self) {
            self.items = anItems;
            self.cellIdentifier = aCellIdentifier;
            self.configureCellBlock = [aConfigureCellBlock copy];
        }
        return self;
    }

    - (id)itemAtIndexPath:(NSIndexPath *)indexPath
    {
        return self.items[(NSUInteger) indexPath.row];
    }

    #pragma mark UITableViewDataSource

    - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
    {
        return self.items.count;
    }

    - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
    {
        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:self.cellIdentifier
                                                        forIndexPath:indexPath];
        id item = [self itemAtIndexPath:indexPath];
        self.configureCellBlock(cell, item);
        return cell;
    }

    @end

使用該dataSource，只需要initWithItems即可，并把該dataSource賦值給tableView.dataSource

    - (void)setupTableView
    {
        TableViewCellConfigureBlock configureCell = ^(PhotoCell *cell, Photo *photo) {
            [cell configureForPhoto:photo];
        };
        NSArray *photos = [AppDelegate sharedDelegate].store.sortedPhotos;
        self.photosArrayDataSource = [[ArrayDataSource alloc] initWithItems:photos
                                                             cellIdentifier:PhotoCellIdentifier
                                                         configureCellBlock:configureCell];
        self.tableView.dataSource = self.photosArrayDataSource;
        [self.tableView registerNib:[PhotoCell nib] forCellReuseIdentifier:PhotoCellIdentifier];
    }

2. 從UIViewController中分離網絡請求

單獨定義一個UIViewControllerData類，實現網絡請求。該類實現UIViewController中定義的協議，在指定時刻去加載數據，進行網絡請求，并把獲取的數據通過調離的block返回給控制器，控制器在進行其他操作（如tableView reload）

.h

    @interface UIViewControllerData : NSObject <RefreshableListViewControllerDataSource>

    + (instancetype)sharedInstance;

    @end

.m

    @implementation UIViewControllerData

    + (instancetype)sharedInstance {
        static UIViewControllerData *instance;
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            instance = [[UIViewControllerData alloc] init];
        });
        return instance;
    }

    - (void)refreshableListViewController:(RefreshableListViewController *)controller loadDataFrom:(NSUInteger)offset limit:(NSUInteger)limit withUserToken:(NSString *)token         completion:(void (^)(NSArray *, BOOL))completionBlock fail:(void (^)(NSError *))failBlock {
        //網絡請求數據
        [UserAPI query:param userToken:token completion:^(NSArray<UserProfileSimplify> *userProfiles, BOOL hasMore) {
                if (completionBlock) {
                    completionBlock(userProfiles,hasMore);
                }
            } error:^(ServerAPIError *error) {
                DDLogDebug(@"---MYLOG:出錯啦！---");
            }];
        } error:failBlock];
    }

    @end