Proper method of editing save-game data

[theCodeCat]

Hi,

For a project I'm working with I want to make sure that save files from old versions can be loaded by new versions.
Since the format in which data is stored may change, I'd like to setup a function that can modify save data after it has been loaded.

To give a basic example, let's say in version 1 an integer value is stored directly in "store.someVar" however in version 2 it gets stored in a wrapper class.
So upon loading a save I'd like something like this to run:

Code: Select all

if store.version == 1:
    store.someVar = Wrapper(store.someVar)

However as I understand it, a save-file doesn't just save the current state, it also saves a history of previous states in case the user wishes to rollback.
And from what I understand from looking at the source, these "states" are chained together and just store how data got changed between them.
So if upon loading a file I want my update code to run on *all* saved states, how would I do that?

(Running the update code everytime a rollback occurs is also an option, but I'd prefer it if it only happens when a file is loaded)

Thanks

[Ocelot]

Did you consider simply blocking rollback past current point in case player loads save file with version mismatch?

[theCodeCat]

Did you consider simply blocking rollback past current point in case player loads save file with version mismatch?

I did. It's an option but it feels like a work-around when I want to know how to do it "properly".

That said, maybe that's the better approach anyway. Rollback history might not be reliable if there have been major version changes