I'd really like to shuffle around the members of struct BuzzData, but I can't because the game assumes old save files conform to that structure layout. We could change the magic number every time we change the save game format, but that's a poor solution. So, let's talk about better solutions.

Protocol Buffers

Protocol Buffers were created to address this need to sanely version data structures.

• Pro: it lets us be explicit about how data should now be laid out without forgetting about how it used to be structured
• Pro: it cleanly separates the definition of an interchange data structure from the code that accesses it
• Pro: it would be particularly appropriate for use over a network (play-by-mail/Internet multiplayer)
• Con: it's another library

jsoncpp

Another option would be to use jsoncpp's coercion and default value support:

m_name = json_object["name"].asString();
m_female = json_object.get("female", false).asBool();
m_capsule = json_object.get("capsule", 0).asInt();
m_lunar = json_object.get("lunar", 0).asInt();
m_eva = json_object.get("eva", 0).asInt();
m_docking = json_object.get("docking", 0).asInt();
m_endurance = json_object.get("endurance", 0).asInt();

• Pro: we already have jsoncpp
• Con: we have to consciously worry about versioning in the code
• Con: ...and we're going to get it wrong somewhere

Even if we pick Protocol Buffers for save games, it shouldn't replace jsoncpp for game data. Game data should be user-editable, and JSON wins there. Moreover, versioning is unimportant since we can to change both the game data and the code that reads it simultaneously. Save games live on-disk, and we're expecting saves to be written by one version and read by another.

Thoughts?