Howdy,
I've become a big fan of @mut throughout my codebase for its
compatibility with closures, but I think it's really biting me in the
ass right now. >.<
Assume there's a state stack (in a state Director) that I'm looping
through to let the states know about an event. In this particular
instance, the event is a key action of ENTER, since 'load_map q3ctf1'
was just typed into the in-game console and ENTER was pressed. The
console state is interested in this event, no doubt.
When the console state gets this load_map command, it'll spring off a
function that creates a game and game_renderer, which are both states
that need to be pushed onto the state stack. But wait! We're currently
looping through the state stack, so trying to add something to it is an
assertion failure on the borrow (BAM, hard failure).
In C++, this could would be perfectly valid, so long as I'm iterating
through the state stack with indices and I'm pushing to the end of it,
thus not affecting the current index. In Rust, this is a big no-no. My
question is: how can I avoid this? Is it just because I'm using @mut
that I'm having this problem? What are some potential solutions that
people can think of, and has anyone hit the same snag in their own code?
Something I have tried: Adding a queue to the state Director of callback
functions (deferred modifications to the states) that states will push
closures onto instead of modifying the Director while it's looping. With
this, the Director could loop through each state, updating it, and then
loop through the queue of deferred callbacks and run them, which would
update the states stack. This didn't work for me since the Director
itself has the borrow lock on it, not just the states stack -- I reckon
I could put the deferred queue into TLS so that I wouldn't need a
mutable reference to the Director to add to it... but there has to be a
better way.
Any tips would be appreciated.
Jeaye
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