Factory pattern: delete child class from memory

[OldBoy]

Working in a project which based in the Factory Pattern,we wanted to remove the child classes from memory as they were too heavy. I had always read that it seemed to be no way to do it. After trying different ideas, I came out with one that spins around of the use of a queue where the data is a class. For this example I used the ‘LV Object’, just trying to do my code the most generic as possible.

 

When I launch my factory, the code does the following:

- Obtains a new one element size queue with a LV Object constant as element data type

- Loads the child using the factory

- Enqueues the new child in the queue using the function 'Lossy queue element'.

 

Obviously, at that moment I had my child in memory, but I discovered that once I released the queue, the child vanished as well from the LV hierarchy, allowing me to load a new child in case I needed, using the factory pattern again. You can find the code attached with the post.

 

As I said I read some posts saying that is not possible to remove the child classes from memory, but this seems to work and I would like to know your opinion, as not being able to run the class hierarchy chart when I run compiled code I cannot ensure that this solution behaves as it seems, although it doesn’t create any errors either.

 

Thanks for your help and time

 

P.S I attach a video where you can see the behaviour of the example

[drjdpowell]

Try adding a method to your child classes.  That seems to make them stay under “Dependancies>>items in memory”.

[OldBoy]

I have tried your idea. You are right. Thank very much indeed for your time and help.

[unicorn]

I think to remember that there is some description by NI that classes are loaded and unloaded if not used any more.

 

I would expect the runtime engine to behave in the same way as the development environment. So if you see a class to be unloaded in the development Environment using the LabVIEW class hierarchy window the same should happen with compiled code.

[JPina]

I think to remember that there is some description by NI that classes are loaded and unloaded if not used any more.

 

I would expect the runtime engine to behave in the same way as the development environment. So if you see a class to be unloaded in the development Environment using the LabVIEW class hierarchy window the same should happen with compiled code.

 

I'd appreciate if you could you tell me where can I find that document.

 

Thank you

[unicorn]

I would have added the link if I would have remembered.

[shoneill]

When I launch my factory, the code does the following:

- Obtains a new one element size queue with a LV Object constant as element data type

- Loads the child using the factory

- Enqueues the new child in the queue using the function 'Lossy queue element'.

 

Obviously, at that moment I had my child in memory, but I discovered that once I released the queue, the child vanished as well from the LV hierarchy, allowing me to load a new child in case I needed, using the factory pattern again. You can find the code attached with the post.

 

That's really cool, I did not know that removing a loaded class was possible.... Must remember this.

[JPina]

That's really cool, I did not know that removing a loaded class was possible.... Must remember this.

 

Actually it is not possible, drjdpowell knocked down the theory...

[Michael Aivaliotis]

Actually it is not possible, drjdpowell knocked down the theory...

 

Agreed. Once a class is loaded into memory, it cannot be unloaded.

 

LabVIEW class factory pattern

[unicorn]

But if you open the class hierarchy window and you can see classes appearing and disappearing, there must be a process to unload classes as well. You cannot force LV manually to unload a  class