optparse: on() vs on_tail()

[James Edward Gray II]

Can someone tell me the difference between the on() and on_tail()
methods of OptionParser. I can't seem to figure it out. Thanks.

James Edward Gray II

 

[Eric Hodel]

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Can someone tell me the difference between the on() and on_tail()
methods of OptionParser. I can't seem to figure it out. Thanks.

from optparse.rb:

=begin
--- OptionParser#on(*opts) [{...}]
--- OptionParser#def_option(*opts) [{...}]
--- OptionParser#on_head(*opts) [{...}]---
OptionParser#def_head_option(*opts) [{...}]
--- OptionParser#on_tail(*opts) [{...}]
--- OptionParser#def_tail_option(*opts) [{...}]
Defines option switch and handler. (({on_head})),
(({def_head_option}))
and (({on_tail})), (({def_tail_option})) put the switch at head
and tail of summary, respectively.

cf. ((<OptionParser#switch>)).
=end #'#"#`#

If you read down from there, on_tail/on add things to the end, of the
args list summary while on_head adds them to the front.

It looks like on_tail only exists to make things pretty.

--
Eric Hodel - (e-mail address removed) - http://segment7.net
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[James Edward Gray II]

If you read down from there, on_tail/on add things to the end, of the
args list summary while on_head adds them to the front.

It looks like on_tail only exists to make things pretty.

Thanks much.

James Edward Gray II

 

[James Edward Gray II]

If you read down from there, on_tail/on add things to the end, of the
args list summary while on_head adds them to the front.

While we're on the subject, if you just use on(), are options added to
the summary in order? Thanks again.

James Edward Gray II

 

[Thomas Kirchner]

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While we're on the subject, if you just use on(), are options added to=20
the summary in order? Thanks again.

Yeah, they're added in the order that you declare them. on_head is useful
for general, common options that most everyone needs, so that they appear
first. on() adds everything to the middle in order. on_tail is good for
generic options like --help or --version that aren't vital, but should be
there. Or at least that's how I use it

There's some decent documentation and a good example here:
http://www.ruby-doc.org/stdlib/libdoc/optparse/rdoc/classes/OptionParser.ht=
ml
Hope that helps.
Tom

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