How to write a function to sync get return value?

[madmongo1]

I need more information to be able to answer your question. Get a return value from what?

[sukeyisme]

net::co_spawn( ioctx.get_executor(), [] { return crawl(); }, net::detached);

This is a async call,If want to get return value sync how to do?

[madmongo1]

the net::detached completion token is causing the return value to be deliberately discarded. You can get the return value type replacing detached with your own lambda or another completion token such as use_awaitable or use_future

So here's one way:

auto f = net::co_spawn(ioctx.get_executor(), crawl(), asio::use_future);
// f is a std::future
f.get();  // block until the future has a value or error

However, you will want to do this on a different thread to the thread that calls run on the io_context

[sukeyisme]

Yes,will have any problem?

[sukeyisme]

how to replacing detached with your own lambda？

Richard Hodges @.***> 于 2021年11月18日周四 17:51写道：

the net::detached completion token is causing the return value to be deliberately discarded. You can get the return value type replacing detached with your own lambda or another completion token such as use_awaitable or use_future

So here's one way:

auto f = net::co_spawn(ioctx.get_executor(), crawl(), asio::use_future); // f is a std::future f.get(); // block until the future has a value or error

However, you will want to do this on a different thread to the thread that calls run on the io_context

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