Cleaning Up After Errors

Whenever an error is raised, it is usually the case that at least some MOO code gets skipped over and never executed. Sometimes, it's important that a piece of code always be executed, whether or not an error is raised. Use the try-finally statement for these cases; it has the following syntax:

try
  statements-1
finally
  statements-2
endtry

First, statements-1 is executed; if it completes without raising an error, returning from this verb, or terminating the current iteration of a surrounding loop (we call these possibilities transferring control), then statements-2 is executed and that's all that happens for the entire try-finally statement.

Otherwise, the process of transferring control is interrupted and statments-2 is executed. If statements-2 itself completes without transferring control, then the interrupted control transfer is resumed just where it left off. If statements-2 does transfer control, then the interrupted transfer is simply forgotten in favor of the new one.

In short, this statement ensures that statements-2 is executed after control leaves statements-1 for whatever reason; it can thus be used to make sure that some piece of cleanup code is run even if statements-1 doesn't simply run normally to completion.

Here's an example:

try
  start = time();
  object:(command)(@arguments);
finally
  end = time();
  this:charge_user_for_seconds(player, end - start);
endtry