Do you keep track of your paths? One of my apps has the ability to
toggle geoAreas that I build out of RMPath objects, which I just keep
in an NSMutableArray called geoPaths. When I want to toggle them, I
simply iterate through the array and change the hidden value:
for(RMPath *path in geoPaths) {
[path setHidden:hiddenBool];
}
I don't see any reason you couldn't do the same, except replacing
setHidden with setLineColor and setFillColor, where the color you set
them to keeps the same RGB values with adjusted alphas. As long as
you don't have obscene amounts of paths this should run fairly
smoothly.