rp5 watch will keep an eye on the source file of your sketch. Whenever you save a change to it, it'll reload your running code, so you can try out your ideas quickly.
rp5 watch is the best way to quickly prototype a sketch.
Ruby-Processing is a playground for live coding. Sketches can be loaded into an interactive code session (IRB) using
rp5 live. Once your sketch is running, the full powers of Ruby metaprogramming are there for you to use. Methods and classes can be redefined on the fly, arguments passed, values changed and all that.
$app will give you a handle to the running sketch. Use it like so:
>> rp5 live samples/jwishy.rb irb(main):001:0> def $app.bluish irb(main):002:1> Math.sin(@y_wiggle) irb(main):003:1> end irb(main):004:0> $app.background = 0.5, 0.5, 0.5, 0.035
This opens up the WishyWorm example in a window, and redefines the
bluish method to return a function of the
y_wiggle. The blue begins to pulse. Then the background is set to be a mostly transparent gray. For ruby-processing-1.0.11 pry was reported as working. It also seems to work with current version but it is a bit flakey in my hands.