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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
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原文地址：http://www.cnblogs.com/fengmin/p/5841009.html
