B4J Question [SOLVED] Sub that became resumablesub

jroriz · Dec 13, 2021

Well, I have (had) a simple sub that returns a value.

This sub will now use the shell, so it has become a resumablesub.

It so happens that I call these sub from various points in my project, and now each sub that calls this resumablesub will also become a resumablesub, forcing me to also change the sub that called it, and so on recursively...

Is there a way to call a resumablesub without making the procedure that calls it resumablesub too?

I made a small example below to clarify the problem...

B4X:

Sub OldSub As ResumableSub    ' it was just a regular sub before the shell
    
    ' now this sub became resumablesub, because it's calling an old sub that became resumablesub
    ' now, all calls to this sub will become resumablesub, and so on...
    
    Wait For (NewSub) complete (r As String)
    Return  r
    
End Sub

Sub NewSub As ResumableSub    ' it was just a regular sub before the shell
    
    ' this sub was not resumablesub, now it's needed.
    Dim sh As Shell
    sh.Initialize("sh","WHAREVER.EXE",Null)
    sh.Run(-1)
    Wait For sh_ProcessCompleted(Success As Boolean, ExitCode As Int, StdOut As String, StdErr As String)

    Return StdOut
End Sub

EnriqueGonzalez · Dec 14, 2021

Well you have 2 options
1. Instead of a wait for, create the normal sub and manage the logic of your app from there

2. Call the shell sub and don't use wait for on the calling sub, just use the called sub to manage your logic

It is a bit of a hazzle but that was the way in the old times

Heuristx · Dec 14, 2021

It is logical that if your Sub waits for something, then it will become a resumable sub itself. It may be puzzling first, because despite of the word "wait", the resumable sub continues the main line of the program immediately(that is, without waiting), but it is worth studying Resumable Subs because they simplify everything when it comes to variable access and eliminate thread locking(!!!). It is crucial to understand Wait For thoroughly. Once you learn what it does, you will appreciate its power. Look at the examples, they may help more than just pondering.

[B4X] Resumable Subs - Sleep / Wait For

New video tutorial: Resumable subs is a new feature added in B4J v5.50 / B4i v4.00 / B4A v7.00. It dramatically simplifies the handling of asynchronous tasks. (This feature is a variant of stackless coroutines.) The special feature of resumable subs is that they can be paused, without...

www.b4x.com

MegatenFreak · Dec 14, 2021

The Resumable Sub "chain reaction" can be annoying, but it's a logical outcome of the "Wait For" concept. Like it was mentioned previously, you could avoid "waiting for" the shell command's completion, letting it work itself in the background, though that itself could create complications.

jroriz · Dec 14, 2021

EnriqueGonzalez said:
Well you have 2 options
1. Instead of a wait for, create the normal sub and manage the logic of your app from there

2. Call the shell sub and don't use wait for on the calling sub, just use the called sub to manage your logic

It is a bit of a hazzle but that was the way in the old times

Thanks for the answers.

1. Instead of a wait for, create the normal sub and manage the logic of your app from there

I don't think it will be possible, because I need the shell, and I need to wait for the result (waitfor). Once you use the shell, you will automatically have a resumablesub.

2. Call the shell sub and don't use wait for on the calling sub, just use the called sub to manage your logic

This would be a huge amount of work, because I would have to move all the logic from the subs that interact with each other to a single sub.
It would be like having a program with a single procedure with no functions...

jroriz · Dec 14, 2021

Heuristx said:
It is logical that if your Sub waits for something, then it will become a resumable sub itself. It may be puzzling first, because despite of the word "wait", the resumable sub continues the main line of the program immediately(that is, without waiting), but it is worth studying Resumable Subs because they simplify everything when it comes to variable access and eliminate thread locking(!!!). It is crucial to understand Wait For thoroughly. Once you learn what it does, you will appreciate its power. Look at the examples, they may help more than just pondering.

[B4X] Resumable Subs - Sleep / Wait For

New video tutorial: Resumable subs is a new feature added in B4J v5.50 / B4i v4.00 / B4A v7.00. It dramatically simplifies the handling of asynchronous tasks. (This feature is a variant of stackless coroutines.) The special feature of resumable subs is that they can be paused, without...

www.b4x.com

See post number 5

jroriz · Dec 14, 2021

MegatenFreak said:
The Resumable Sub "chain reaction" can be annoying, but it's a logical outcome of the "Wait For" concept. Like it was mentioned previously, you could avoid "waiting for" the shell command's completion, letting it work itself in the background, though that itself could create complications.

See post number 5

Erel · Dec 14, 2021

Once you understand how resumable subs work you will understand that this chain of resumable subs is part of the design. There is no way around it (unless you are fine with the code flow continuing without waiting for the sub to complete).
The benefits of resumable subs are huge. They change the way we program.

Simply change the calls to use Wait For. It will not take you more than 5 minutes to do...

jroriz · Dec 14, 2021

Erel said:
Once you understand how resumable subs work you will understand that this chain of resumable subs is part of the design. There is no way around it (unless you are fine with the code flow continuing without waiting for the sub to complete).
The benefits of resumable subs are huge. They change the way we program.

Simply change the calls to use Wait For. It will not take you more than 5 minutes to do...

In fact, what happened was the following:
The project has been around for a few years now, and it's a HUD, which displays poker information on the screen, and it's a pretty complex project.
There was a sub that read information only from the screen, many parts of the program use this sub.
It is now necessary to call an external application to process this screen information.
That's what generated these cascading changes.
I understand how resumablesub works and its benefits.
But if there was a way (which I've seen that there isn't) to use wait for without the calling routine turning into a resumablesub too, it would save me a lot of work.
Thank you all.

EnriqueGonzalez · Dec 14, 2021

you could try something like

B4X:

private sub resumable_shell(obj as object, method as string)
  shell...
  shell...
  result = shell...

  callsubdelayed(obj,method,result)
end sub

private sub a
   shell(me, "a2")
end sub

private sub a2(result)

end sub

private sub b
 shell(me, "b2")
end sub

private sub b2(result)

end sub

private sub c
 shell(me, "c2")
end sub

private sub c2(result)

end sub

jroriz · Dec 14, 2021

EnriqueGonzalez said:

you could try something like

B4X:

private sub resumable_shell(obj as object, method as string)
  shell...
  shell...
  result = shell...

  callsubdelayed(obj,method,result)
end sub

private sub a
   shell(me, "a2")
end sub

private sub a2(result)

end sub

private sub b
 shell(me, "b2")
end sub

private sub b2(result)

end sub

private sub c
 shell(me, "c2")
end sub

private sub c2(result)

end sub

I did not understand...
Could you "translate" using the code from post #1?

EnriqueGonzalez · Dec 14, 2021

B4X:

Sub OldSub
   
    ' now this sub became resumablesub, because it's calling an old sub that became resumablesub
    ' now, all calls to this sub will become resumablesub, and so on...
   
    NewSub(me,"OldSub2")
End Sub

sub OldSub2(expected_value)
    log(expected_value)
end sub

Sub NewSub(obj as object, method as string)   ' it was just a regular sub before the shell
   
    ' this sub was not resumablesub, now it's needed.
    Dim sh As Shell
    sh.Initialize("sh","WHAREVER.EXE",Null)
    sh.Run(-1)
    Wait For sh_ProcessCompleted(Success As Boolean, ExitCode As Int, StdOut As String, StdErr As String)

    callsubdelayed(me, method,stdOut)
End Sub

jroriz · Dec 14, 2021

EnriqueGonzalez said:

B4X:

Sub OldSub
  
    ' now this sub became resumablesub, because it's calling an old sub that became resumablesub
    ' now, all calls to this sub will become resumablesub, and so on...
  
    NewSub(me,"OldSub2")
End Sub

sub OldSub2(expected_value)
    log(expected_value)
end sub

Sub NewSub(obj as object, method as string)   ' it was just a regular sub before the shell
  
    ' this sub was not resumablesub, now it's needed.
    Dim sh As Shell
    sh.Initialize("sh","WHAREVER.EXE",Null)
    sh.Run(-1)
    Wait For sh_ProcessCompleted(Success As Boolean, ExitCode As Int, StdOut As String, StdErr As String)

    callsubdelayed(me, method,stdOut)
End Sub

That's it!
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