使用ReactiveCocoa开发RSS阅读器

目前已经完成的功能有对RSS的解析和Atom解析，RSS内容本地数据库存储和读取，抓取中状态进度展示，标记阅读状态，标记全部已读等。这些功能里我对一些异步操作产生的数据采用了ReactiveCocoa来对数据流向进行了控制，下面我来说下如何运用RAC来进行的开发。

初始时读取本地存储首页列表数据，过滤无效数据，监听列表数据变化进行列表更新

这里会用到RAC这个宏可以方便的来进行键值和信号的绑定，RACObserve这个宏方便的进行键值变化的监听处理。具体实现代码如下：

@weakify(self);

//首页列表数据赋值，过滤无效数据

RAC(self, feeds) = [[[SMDB shareInstance] selectAllFeeds] filter:^BOOL(NSMutableArray *feedsArray) {

if (feedsArray.count > 0) {

return YES;

} else {

return NO;

}

}];

//监听列表数据变化进行列表更新

[RACObserve(self, feeds) subscribeNext:^(id x) {

@strongify(self);

[self.tableView reloadData];

}];

//本地读取首页订阅源数据

- (RACSignal *)selectAllFeeds {

@weakify(self);

return [RACSignal createSignal:^RACDisposable *(id subscriber) {

@strongify(self);

FMDatabase *db = [FMDatabase databaseWithPath:self.feedDBPath];

if ([db open]) {

FMResultSet *rs = [db executeQuery:@"select * from feeds"];

NSUInteger count = 0;

NSMutableArray *feedsArray = [NSMutableArray array];

while ([rs next]) {

SMFeedModel *feedModel = [[SMFeedModel alloc] init];

feedModel.fid = [rs intForColumn:@"fid"];

feedModel.title = [rs stringForColumn:@"title"];

feedModel.link = [rs stringForColumn:@"link"];

feedModel.des = [rs stringForColumn:@"des"];

feedModel.copyright = [rs stringForColumn:@"copyright"];

feedModel.generator = [rs stringForColumn:@"generator"];

feedModel.imageUrl = [rs stringForColumn:@"imageurl"];

feedModel.feedUrl = [rs stringForColumn:@"feedurl"];

feedModel.unReadCount = [rs intForColumn:@"unread"];

[feedsArray addObject:feedModel];

count++;

}

[subscriber sendNext:feedsArray];

[subscriber sendCompleted];

[db close];

}

return nil;

}];

}

通过网络获取订阅源最新内容，获取后进行本地存储，转成显示用的model进行列表的显示

这里的异步操作比较多，而且为了尽快取得数据采用的是并行队列，需要准确的获取到每个源完成的状态，包括解析的完成，本地存储完成，全部获取完成等数据完成情况。具体使用RAC方式的代码如下：

//获取所有feeds以及完成处理

- (void)fetchAllFeeds {

[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;

self.tableView.tableHeaderView = self.tbHeaderView;

self.fetchingCount = 0; //统计抓取数量

@weakify(self);

[[[[[[SMNetManager shareInstance] fetchAllFeedWithModelArray:self.feeds] map:^id(NSNumber *value) {

@strongify(self);

NSUInteger index = [value integerValue];

self.feeds[index] = [SMNetManager shareInstance].feeds[index];

return self.feeds[index];

}] doCompleted:^{

//抓完所有的feeds

@strongify(self);

NSLog(@"fetch complete");

//完成置为默认状态

self.tbHeaderLabel.text = @"";

self.tableView.tableHeaderView = [[UIView alloc] init];

self.fetchingCount = 0;

[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;

}] deliverOn:[RACScheduler mainThreadScheduler]] subscribeNext:^(SMFeedModel *feedModel) {

//抓完一个

@strongify(self);

//显示抓取状态

self.fetchingCount += 1;

self.tbHeaderLabel.text = [NSString stringWithFormat:@"正在获取%@...(%lu/%lu)",feedModel.title,(unsigned long)self.fetchingCount,(unsigned long)self.feeds.count];

[self.tableView reloadData];

}];

}

//网络获取以及解析本地存储

- (RACSignal *)fetchAllFeedWithModelArray:(NSMutableArray *)modelArray {

@weakify(self);

return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {

@strongify(self);

//创建并行队列

dispatch_queue_t fetchFeedQueue = dispatch_queue_create("com.starming.fetchfeed.fetchfeed", DISPATCH_QUEUE_CONCURRENT);

dispatch_group_t group = dispatch_group_create();

self.feeds = modelArray;

for (int i = 0; i < modelArray.count; i++) {

dispatch_group_enter(group);

SMFeedModel *feedModel = modelArray[i];

dispatch_async(fetchFeedQueue, ^{

[self GET:feedModel.feedUrl parameters:nil progress:nil success:^(NSURLSessionTask *task, id responseObject) {

//解析feed

self.feeds[i] = [self.feedStore updateFeedModelWithData:responseObject preModel:feedModel];

//入库存储

SMDB *db = [[SMDB alloc] init];

[[db insertWithFeedModel:self.feeds[i]] subscribeNext:^(NSNumber *x) {

SMFeedModel *model = (SMFeedModel *)self.feeds[i];

model.fid = [x integerValue];

//插入本地数据库成功后开始sendNext

[subscriber sendNext:@(i)];

//通知单个完成

dispatch_group_leave(group);

}];

} failure:^(NSURLSessionTask *operation, NSError *error) {

NSLog(@"Error: %@", error);

dispatch_group_leave(group);

}];

});//end dispatch async

}//end for

//全完成后执行事件

dispatch_group_notify(group, dispatch_get_main_queue(), ^{

[subscriber sendCompleted];

});

return nil;

}];

}

读取RSS列表，异步读取，主线程更新

这里通过RAC能够很方便的进行主线程操作UI，非主线程操作数据这样的操作，具体实现如下：

//获取列表数据以及对应的操作

- (void)selectFeedItems {

RACScheduler *scheduler = [RACScheduler schedulerWithPriority:RACSchedulerPriorityHigh];

@weakify(self);

[[[[[SMDB shareInstance] selectFeedItemsWithPage:self.page fid:self.feedModel.fid]

subscribeOn:scheduler]

deliverOn:[RACScheduler mainThreadScheduler]]

subscribeNext:^(NSMutableArray *x) {

@strongify(self);

if (self.listData.count > 0) {

//进入时加载

[self.listData addObjectsFromArray:x];

} else {

//加载更多

self.listData = x;

}

//刷新

[self.tableView reloadData];

} error:^(NSError *error) {

//处理无数据的显示

[self.tableView.mj_footer endRefreshingWithNoMoreData];

} completed:^{

//加载完成后的处理

[self.tableView.mj_footer endRefreshing];

}];

self.page += 1;

}

//数据库获取信号

- (RACSignal *)selectFeedItemsWithPage:(NSUInteger)page fid:(NSUInteger)fid {

@weakify(self);

return [RACSignal createSignal:^RACDisposable *(id subscriber) {

@strongify(self);

FMDatabase *db = [FMDatabase databaseWithPath:self.feedDBPath];

if ([db open]) {

//分页获取

FMResultSet *rs = [db executeQuery:@"select * from feeditem where fid = ? and isread = ? order by iid desc limit ?, 20",@(fid), @(0), @(page * 20)];

NSUInteger count = 0;

NSMutableArray *feedItemsArray = [NSMutableArray array];

//设置返回Array里的Model

while ([rs next]) {

SMFeedItemModel *itemModel = [[SMFeedItemModel alloc] init];

itemModel.iid = [rs intForColumn:@"iid"];

itemModel.fid = [rs intForColumn:@"fid"];

itemModel.link = [rs stringForColumn:@"link"];

itemModel.title = [rs stringForColumn:@"title"];

itemModel.author = [rs stringForColumn:@"author"];

itemModel.category = [rs stringForColumn:@"category"];

itemModel.pubDate = [rs stringForColumn:@"pubDate"];

itemModel.des = [rs stringForColumn:@"des"];

itemModel.isRead = [rs intForColumn:@"isread"];

[feedItemsArray addObject:itemModel];

count++;

}

if (count > 0) {

[subscriber sendNext:feedItemsArray];

} else {

//获取出错处理

[subscriber sendError:nil];

}

[subscriber sendCompleted];

[db close];

}

return nil;

}];

}

完整代码可以在这里看:https://github.com/ming1016/GCDFetchFeed