我所试图做的是一个网站包装为Facebook的iOS SDK。 基本想法是,我的ViewController应该做什么,但呈现前。 我的朋友们,将用一个简单的调用来获取像
self.friends = [FacebookWrapper myFriends];
[self.tableView reloadData];
我的包装myFriends方法应该是这样的
+ (NSArray *)myFriends
{
__block NSArray *friends = nil;
[FBSession openActiveSessionWithReadPermissions:nil allowLoginUI:YES completionHandler:^(FBSession *session, FBSessionState status, NSError *error) {
if(FB_ISSESSIONOPENWITHSTATE(status)) {
[FBRequestConnection startForMyFriendsWithCompletionHandler:^(FBRequestConnection *connection, id data, NSError *error) {
CFRunLoopStop(CFRunLoopGetCurrent());
if(error) {
return;
}
NSArray *friendsData = (NSArray *)[data data];
NSMutableArray *fbFriends = [NSMutableArray array];
for(id friendData in friendsData) {
Friend *friend = [Friend friendWithDictionary:friendData];
fbFriends addObject:friend];
}
friends = [NSArray arrayWithArray:fbFriends];
}];
CFRunLoopRun();
}
}];
return friends;
}
问题是,openActiveSessionWithReadPermissions和startForMyFriendsWithCompletionHandler是异步块,这样的方法会返回块完成他们的任务之前。
任何帮助将非常感激。
我在过去创建了类似的包装,并调用我的包装方法时,我的方法是传递一个“完成块”; 那么这个完成块被触发一次所有的异步调用完成后运行,它接收所有数据的方法将在同步情况下返回(在你的情况下,朋友阵列)。
为了说明 - 你可以有你的“myFriends”的方法重新定义为:
+ (void)myFriendsWithCompletionBlock:(void (^)(NSArray *friends))completionBlock;
然后在实施中,之后friends = [NSArray arrayWithArray:fbFriends];
行,你想补充一点:
if (completionBlock != nil) {
completionBlock(friends);
}
...并删除return
在最后陈述。
最后,您的视图控制器(或使用该方法的对象上,你会做这样的事情:
[FacebookWrapper myFriendsWithCompletionBlock:^(NSArray *friends){
// do what you need to do with the friends array
}];
当然,这仍然是异步的 - 但有周围没有办法,因为这是Facebook的SDK如何编译(和,说句公道话,这可能是做到这一点的最好办法 - 等待请求完成同步将是可怕的!)
编辑:我注意到你也的情况下,失败的包装方法返回; 在这种情况下,而不是返回你会做这样的事情的:
if (completionBlock != nil) {
completionBlock(nil);
}
这将导致friends
阵列是nil
,当你完成块被称为-那么你可以把这个错误但有似乎是适当的给你。
希望这有助于!
如果你分派asynchronouos块,你可以与你沟通UIViewController
通过回调它的子类:
[self someSelectorWithCallbackData:stuffWhichYouWantToGiveBack];
这将调用self
获得由块捕获,因此将正常工作。 从相关的方法,你可以刷新视图/重装的tableview /所需跳舞的夹具。
根据上下文,您可能需要__block
范围self
,如
__block UIViewController *bsself = self;
但是,如果你是后者,要小心避免保留环(构建和分析工具是在指出这一点相当不错)。
认为你需要使用protol @class Webservice的;
@protocol WebserviceDelegate
@optional
-(void)webservice:(Webservice *)webservice didFetchPosts:(NSArray *)posts;
-(void)webservice:(Webservice *)webservice didFetchComments:(NSArray *)comments forPostID:(NSString *)postID launchComments:(BOOL)launch;
-(void)webservice:(Webservice *)webservice didLoginWithUser:(User *)user;
-(void)webservice:(Webservice *)webservice didVoteWithSuccess:(BOOL)success forObject:(id)object direction:(BOOL)up;
@end
@interface Webservice : NSObject {
__weak id <WebserviceDelegate> delegate;
}
//Delegate
@property (weak) id <WebserviceDelegate> delegate;
-(void)getHomepage {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
NSURLResponse *response;
NSError *error;
// Create the URL Request
NSMutableURLRequest *request = [Webservice NewGetRequestForURL:[NSURL URLWithString:@"https://www.hnsearch.com/bigrss"]];
// Start the request
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
//Handle response
//Callback to main thread
if (responseData) {
NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSStringEncodingConversionAllowLossy];
if (responseString.length > 0) {
dispatch_async(dispatch_get_main_queue(), ^{
[self parseIDsAndGrabPosts:responseString];
});
}
else {
dispatch_async(dispatch_get_main_queue(), ^{
[delegate webservice:self didFetchPosts:nil];
});
}
}
else {
dispatch_async(dispatch_get_main_queue(), ^{
[delegate webservice:self didFetchPosts:nil];
});
}
});
}
-(void)parseIDsAndGrabPosts:(NSString *)parseString {
// Parse String and grab IDs
NSMutableArray *items = [@[] mutableCopy];
NSArray *itemIDs = [parseString componentsSeparatedByString:@"<hnsearch_id>"];
for (int xx = 1; xx < itemIDs.count; xx++) {
NSString *idSubString = itemIDs[xx];
[items addObject:[idSubString substringWithRange:NSMakeRange(0, 13)]];
}
// Send IDs back to HNSearch for Posts
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
NSURLResponse *response;
NSError *error;
// Create Request String
NSString *requestString = @"http://api.thriftdb.com/api.hnsearch.com/items/_bulk/get_multi?ids=";
for (NSString *item in items) {
requestString = [requestString stringByAppendingString:[NSString stringWithFormat:@"%@,", item]];
}
// Create the URL Request
NSMutableURLRequest *request = [Webservice NewGetRequestForURL:[NSURL URLWithString:requestString]];
// Start the request
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
//Handle response
//Callback to main thread
if (responseData) {
NSArray *responseArray = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingAllowFragments error:&error];
if (responseArray) {
NSMutableArray *postArray = [@[] mutableCopy];
for (NSDictionary *dict in responseArray) {
[postArray addObject:[Post postFromDictionary:dict]];
}
NSArray *orderedPostArray = [self orderPosts:postArray byItemIDs:items];
dispatch_async(dispatch_get_main_queue(), ^{
[delegate webservice:self didFetchPosts:orderedPostArray];
// Update Karma for User
if ([HNSingleton sharedHNSingleton].User) {
[self reloadUserFromURLString:[NSString stringWithFormat:@"https://news.ycombinator.com/user?id=%@", [HNSingleton sharedHNSingleton].User.Username]];
}
});
}
else {
dispatch_async(dispatch_get_main_queue(), ^{
[delegate webservice:self didFetchPosts:nil];
});
}
}
else {
dispatch_async(dispatch_get_main_queue(), ^{
[delegate webservice:self didFetchPosts:nil];
});
}
});
}