Ruby hackery needed
Here’s a kind of code I find myself habitually writing until I realize I can’t implement it:
watch {
# some calculation
}.and_whenever(:something_happened) {
# do something
}.and_whenever(:something_else_happened) {
# do something else
}
What I want this to do is:
-
Stash away the block with “some calculation”
-
Run the second block. This does something that will affect the calculation.
-
Run the third block. This does something else that will affect the calculation.
-
Run the first block, then undo the effects of the following blocks.
The problem is that I don’t see a way to know when you’ve reached the end of the chain of 2nd, 3rd, … blocks, and it’s now time to execute the first block.
Now, there are alternatives. You can put the blocks in the right order. You can make a single and_whenever that takes a hash from names to lambdas as its single argument (presuming the order of evaluation doesn’t matter). You can put a “sentinel” method at the end of the chain, like .ok_do_it_now.
What I’m wondering if there’s some clever way of making the original form work.
October 8th, 2007 at 1:38 pm
Have a look at http://god.rubyforge.org They have a syntax that is close to this:
God.watch do |w|
w.oncondition(:some_condition) do
end
end
And you could probably do this with AOP: http://aquarium.rubyforge.org/examples.html