Ruby has iterators/generators. It doesn't have first-class functions because it doesn't have functions at all, but blocks/procs serve the same purposes.
Blocks are sort of like anonymous function literals that are not first class, one (but no more than one) of which may be attached to a function call.
Blocks are a syntactically special single argument to a method that can either be yielded to (a Ruby construct similar to a function call but which only applies to the block passed to the current method) or converted to a proc (but the latter only as part of the method definition, since they aren't first class and thus cannot be manipulated or referred to directly.)