Infinite yields from an iterator

Question

I'm trying to learn some ruby. Imagine I'm looping and doing a long running process, and in this process I want to get a spinner for as long as necessary.

So I could do:

a=['|','/','-','\\']
aNow=0
# ... skip setup a big loop
print a[aNow]
aNow += 1
aNow = 0 if aNow == a.length
# ... do next step of process
print "\b"

But I thought it'd be cleaner to do:

def spinChar
  a=['|','/','-','\\']
  a.cycle{|x| yield x}
end
# ... skip setup a big loop
print spinChar
# ... do next step of process
print "\b"

Of course the spinChar call wants a block. If I give it a block it'll hang indefinitely.

How can I get just the next yeild of this block?

Answer 1

Ruby's yield does not work in the way your example would like. But this might be a good place for a closure:

def spinner()
  state = ['|','/','-','\\']
  return proc { state.push(state.shift)[0] }
end

spin = spinner

# start working
print spin.call
# more work
print spin.call
# etc...

In practice I think this solution might be too "clever" for its own good, but understanding the idea of Procs could be useful anyhow.