New in version 2.0.
Yield components in spanner one at a time from left to right.
abjad> t = Staff("c'8 d'8 e'8 f'8")
abjad> p = spannertools.BeamSpanner(t[2:])
abjad> notes = spannertools.iterate_components_forward_in_spanner(p, klass = Note)
abjad> for note in notes:
... note
Note("e'8")
Note("f'8")
Changed in version 2.0: renamed spannertools.iterate_components_forward() to spannertools.iterate_components_forward_in_spanner().