# Hash#getopt

**URL:** <https://www.ruby-forum.com/t/hash-getopt/94195>\
**Category:** Ruby\
**Created:** [April 25, 2006, 5:21am UTC](https://www.ruby-forum.com/t/hash-getopt/94195 "2006-04-25T05:21:13Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [April 25, 2006, 5:21am UTC](https://www.ruby-forum.com/t/hash-getopt/94195/1 "2006-04-25T05:21:13Z")

</div>

at this point calls of the form

some\_method arg, “key” =\> “value”

or

some\_method arg, :key=\>:value

are idiomatic ruby. let’s just support it directly and be done with it:

```
 harp:~ > cat a.rb
 class ::Hash
   def getopt opt, default = nil
     keys = opt.respond_to?('each') ? opt : [opt]
     keys.each do |key, *ignored|
       return self[key] if self.has_key? key
       key = "#{ key }"
       return self[key] if self.has_key? key
       key = key.intern
       return self[key] if self.has_key? key
     end
     return default
   end
 end

 opts = {'k' => 42}
   p opts.getopt('k')
   p opts.getopt(:k)

 opts = {:k => 42}
   p opts.getopt('k')
   p opts.getopt(:k)

 opts = {'K' => 42}
   p opts.getopt('k', opts.getopt('K'))
   p opts.getopt(:k, opts.getopt(:K))
   p opts.getopt(%w( k K ))

 opts = {:K => 42}
   p opts.getopt('k', opts.getopt('K'))
   p opts.getopt(:k, opts.getopt(:K))
   p opts.getopt(%w( k K ))

 harp:~ > ruby a.rb
 42
 42
 42
 42
 42
 42
 42
 42
 42
 42

```

regards.

-a

---

<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [April 25, 2006, 5:33am UTC](https://www.ruby-forum.com/t/hash-getopt/94195/2 "2006-04-25T05:33:44Z")

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Hi –

On Tue, 25 Apr 2006, removed\_email\_address@domain.invalid wrote:

> at this point calls of the form
> 
> some\_method arg, “key” =\> “value”
> 
> or
> 
> some\_method arg, :key=\>:value
> 
> are idiomatic ruby. let’s just support it directly and be done with it:

Can you editorialize a little more? 🙂 I’m not clear on the  
connection between the above and the below. Are you mainly interested  
in having hashes that don’t differentiate between string and symbol  
keys?

David

–  
David A. Black (removed\_email\_address@domain.invalid)  
Ruby Power and Light, LLC ([http://www.rubypowerandlight.com](http://www.rubypowerandlight.com))

“Ruby for Rails” PDF now on sale! [Ruby for Rails](http://www.manning.com/black)  
Paper version coming in early May!

---

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**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [April 25, 2006, 5:48am UTC](https://www.ruby-forum.com/t/hash-getopt/94195/3 "2006-04-25T05:48:53Z")

</div>

On Tue, 25 Apr 2006 removed\_email\_address@domain.invalid wrote:

> > some\_method arg, :key=\>:value
> > 
> > are idiomatic ruby. let’s just support it directly and be done with it:
> 
> Can you editorialize a little more? 🙂 I’m not clear on the  
> connection between the above and the below. Are you mainly interested  
> in having hashes that don’t differentiate between string and symbol  
> keys?

yes, but **only** for the getopt method. mainly i’m campaigning for a  
Hash#getopt method to support people writing friendly apis that can be  
used  
like this

spawn cmd, :stdin =\> buf

or

spawn cmd, ‘stdin’ =\> buf

given a def like

def spawn cmd, opts = {}  
stdin = opts.getopt :stdin  
…  
end

i think that when getting and option from a hash, and only when getting  
an  
option from a hash, we should be able to use strings or symbols and  
provide a  
default value. note that we cannot use short-circuit operator for  
default  
here since

def some\_method arg, opts = {}  
quiet = opts.getopt(:quiet) || true  
end

would fail with

some\_method 42, :quiet =\> false

and hence Hash#getopt also requires the optional ‘default’ param so  
useage  
may, instead, be

def some\_method arg, opts = {}  
quiet = opts.getopt(:quiet, true)  
end

followed by

some\_method 42, :quiet =\> false

and this then behaves correctly.

make more sense?

regards.

-a

---

<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [April 25, 2006, 6:04am UTC](https://www.ruby-forum.com/t/hash-getopt/94195/4 "2006-04-25T06:04:09Z")

</div>

Hi –

On Tue, 25 Apr 2006, removed\_email\_address@domain.invalid wrote:

> end
> 
> followed by
> 
> some\_method 42, :quiet =\> false
> 
> and this then behaves correctly.
> 
> make more sense?

Yes. I’m not sure how I’ll vote when it appears on RCRchive 🙂 (I’m  
not big on the symbol \<=\> string indifference thing, though I can see  
where having a particular access method that uses it could be useful.)

David

–  
David A. Black (removed\_email\_address@domain.invalid)  
Ruby Power and Light, LLC ([http://www.rubypowerandlight.com](http://www.rubypowerandlight.com))

“Ruby for Rails” PDF now on sale! [Ruby for Rails](http://www.manning.com/black)  
Paper version coming in early May!

---

<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [April 25, 2006, 6:25am UTC](https://www.ruby-forum.com/t/hash-getopt/94195/5 "2006-04-25T06:25:42Z")

</div>

On Tue, 25 Apr 2006, Brian M. wrote:

> Brian.

i agree. however, consider that they are really two orthogonal ideas:

```
 harp:~ > cat a.rb
 class ::Hash
   def getopt opt, default = nil
     keys = opt.respond_to?('each') ? opt : [opt]
     keys.each do |key, *ignored|
       return self[key] if self.has_key? key
       key = "#{ key }"
       return self[key] if self.has_key? key
       key = key.intern
       return self[key] if self.has_key? key
     end
     return default
   end
 end

 require 'yaml'

 config = YAML::load <<-conf

   host : codeforpeople.com
   port : 80
   path : /lib/ruby

 conf

 p config.getopt(:host)
 p config.getopt(:protocol, 'http')

 harp:~ > ruby a.rb
 "codeforpeople.com"
 "http"

```

there are often times where a hash is used in ruby as a bundle of  
options/attributes, in these cases it’s often useful to offer  
symbol/string  
indifferent access. and, even if keyword arguments are supported, i’m  
sure  
hash-style interfaces will remain for quite a while - there are simply  
too many  
of them out there already.

cheers.

-a

---

<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [April 26, 2006, 4:04pm UTC](https://www.ruby-forum.com/t/hash-getopt/94195/6 "2006-04-26T16:04:25Z")

</div>

removed\_email\_address@domain.invalid wrote:

> > make more sense?
> 
> Yes. I’m not sure how I’ll vote when it appears on RCRchive 🙂 (I’m  
> not big on the symbol \<=\> string indifference thing, though I can see  
> where having a particular access method that uses it could be useful.)

David, can you elaborate a little more. I’m interested in why you are  
“not big of the symbol \<=\> string indifference thing”.

---

<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [April 25, 2006, 6:13am UTC](https://www.ruby-forum.com/t/hash-getopt/94195/7 "2006-04-25T06:13:29Z")

</div>

On 4/24/06, removed\_email\_address@domain.invalid [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> end
> 
> followed by
> 
> some\_method 42, :quiet =\> false
> 
> and this then behaves correctly.
> 
> make more sense?

I think it makes sense, but we need to consider that, as far as 2.0 is  
concerned, there will probably be other solutions/options. I am  
talking about keyword arguments. I may have been one in the minority  
but I liked Matz’s idea for keyword arguments.

With this sort of future addition one could question the need of  
adding this to Hash. I can’t say I am on either side yet. I think it  
might be time to evaluate what is really useful about hash arguments  
that keyword arguments won’t handle (nicely). It might come down to  
TIMTOWTDI or backwards compatibility.

Brian.