Yielding is not allowed within a C or metamethod call

[optimator999]

The way I'm developing my plug in is that I'm creating individual modules, testing those modules and then integrating the modules into my plugin. The individual modules work. However, I have a problem when I try to integrate.

I'm using an anonymous function to call a function when a user presses a button. That function calls another lua file (is that a module?) If I place the require statement at the top of the file I receive the Yielding is not allowed within a C or metamethod call error.

However, if I place the require statement within the function that specifically requires accessing the lua file then I don't receive the error. Clearly, I don't understand what's going on. Can anyone explain what is happening here?

Thanks!

[areohbee]

Does your module have executable code in the body of it? If so, consider putting it in a function, then call the function when you are ready, so nothing gets executed when the module is "require'd".

[optimator999]

Hey Rob,

Thanks for helping me with this. Since this is so new to me, I'm all over the place and I'm having trouble even understanding what my problems are 🙂

Anyway, here's where I'm at:

I have a button in sectionsForTopOfDialog. I have changed the action to be action = function() .... end

When I press the button the function is called. The problem is when I call the LrHttp.post function. That's when the yield error is being thrown.

[johnrellis · Accepted solution]

The problem is when I call the LrHttp.post function. That's when the yield error is being thrown.

The error message "Yielding is not allowed within a C or metamethod call" arises when you call a function or method that needs to be invoked from a task created by LrTasks or LrFunctionContext.postAsyncTaskWithContext.

In this case, the LrHttp functions have to be called from a task.  The SDK documentation is pretty good (but not perfect) about calling out which functions and methods have to be called from a task. 

[optimator999]

Thanks! Of course, that was my problem.

[areohbee]

try:

action = function( button )

     -- start task

end

instead of:

action = "call a function that starts a task"

In the first case, you are assigning a function value to action which will get called when the user clicks the button.

In the second case, you are calling a function and assigning the return value to action.

eh?

R