CODEWITHSUNDEEP
c++windows-8windows-runtimetask-parallel-libraryppl
Shahar Prish
Shahar Prish

Reputation: 4849

In VC++ PPL, how do I create a task-returning method that returns synchronously?

Consider the following C# code:

async Task DoSomethingAsync()
{
 if (m_f)
   return;
 await DoSomethingInternalAsync();
}

What the compiler turns this into is a task returning call where if m_f is true, the task completes immediately and if not, it "delegates" the async operation to DoSomethingInternalAsync().

Now, how do I do this in c++? The code should look something like this:

task<void> DoSomethingAsync()
{
if (m_f)
   return [[What do I return here so the task is complete (.then called immediately)?!]];
return DoSomethingInternalAsync();
}

Edit1: In C#, I can use a TaskCompletionSource<> to do the same thing, but w/o using the async keyword - essentially create a completed Task.

Upvotes: 3

Views: 2295

Answers (2)

bobbymcr
bobbymcr

Reputation: 24167

Another way to do this is task_from_result. You can use concurrency::task_from_result() for task<void> methods and concurrency::task_from_result(theReturnValue) for task<T> methods. I believe this is new starting in Visual Studio 2013.

Upvotes: 10

Shahar Prish
Shahar Prish

Reputation: 4849

Got it.. This will create an empty task:

concurrency::create_task([]{});

Upvotes: 2

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