本文介绍了使 iOS 块同步执行的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着跟版网的小编来一起学习吧！
问题描述
如何让一个block同步执行，或者让函数在return语句之前等待handler，这样数据才能从block传回来?
How can I make a block execute synchronously, or make the function wait for the handler before the return statement, so the data can be passed back from the block?
-(id)performRequest:(id)args
{
__block NSData *data = nil;
[xyzclass requestAccessToAccountsWithType:accountType withCompletionHandler:^(BOOL granted, NSError *error) {
data = [NSData dataWithData:responseData];
}];
return data;
}
推荐答案
在这种情况下你可以使用信号量.
You can use semaphores in this case.
-(id)performRequest:(id)args
{
__block NSData *data = nil;
dispatch_semaphore_t sem = dispatch_semaphore_create(0);
[xyzclass requestAccessToAccountsWithType:accountType withCompletionHandler:^(BOOL granted, NSError *error) {
data = [NSData dataWithData:responseData];
dispatch_semaphore_signal(sem);
}];
dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
return data;
}
信号量将阻止进一步语句的执行，直到收到信号，这将确保您的函数不会过早返回.
semaphore will block execution of further statements until signal is received, this will make sure that your function does not return prematurely.
这篇关于使 iOS 块同步执行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！
本站部分内容来源互联网,如果有图片或者内容侵犯了您的权益，请联系我们，我们会在确认后第一时间进行删除！