在下面的函数中,我一直得到:
变量不可分配(缺少__block类型说明符)
我尝试通过将__block
添加到twitterUsername
来修复它,但该函数返回null
。我究竟做错了什么?我真的很想了解这背后的逻辑,而不仅仅是解决方案。
- (NSString *) getTwitterAccountInformation
{
ACAccountStore *accountStore = [[ACAccountStore alloc] init];
ACAccountType *accountType = [accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierTwitter];
NSString *twitterUsername = [[NSString alloc] init];
[accountStore requestAccessToAccountsWithType:accountType
options:nil
completion:^(BOOL granted, NSError *error)
{
if(granted) {
NSArray *accountsArray = [accountStore accountsWithAccountType:accountType];
if ([accountsArray count] > 0) {
ACAccount *twitterAccount = [accountsArray objectAtIndex:0];
NSLog(@"%@",twitterAccount.username);
NSLog(@"%@",twitterAccount.accountType);
twitterUsername = [NSString stringWithFormat:@"%@", twitterAccount.username];
}
}
}];
NSLog(@"Twitter username is: %@", twitterUsername);
return twitterUsername;
}
答案 0 :(得分:1)
requestAccessToAccountsWithType:options:completion:
方法是异步的,这意味着它不会等待对网络调用的响应,并立即返回。
相反,它会在调用返回后将一个块排入队列,并在数据加载后执行它。
一种可能的解决方案是让你的getTwitterAccountInformation
也将完成块作为参数,这可能如下所示:
- (void) getTwitterAccountInformation:(void(^)(NSString *userName, NSError *error))completion
{
ACAccountStore *accountStore = [[ACAccountStore alloc] init];
ACAccountType *accountType = [accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierTwitter];
[accountStore requestAccessToAccountsWithType:accountType options:nil completion:^(BOOL granted, NSError *error) {
if(error) {
completion(nil, error);
}
if(granted) {
NSArray *accountsArray = [accountStore accountsWithAccountType:accountType];
if ([accountsArray count] > 0) {
ACAccount *twitterAccount = [accountsArray objectAtIndex:0];
NSLog(@"%@",twitterAccount.username);
NSLog(@"%@",twitterAccount.accountType);
NSString *twitterUsername = twitterAccount.username;
NSLog(@"Twitter username is: %@", twitterUsername);
completion(twitterUsername, nil);
}
}
}];
}