Preferred method of dealing with options in final argument hash

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Preferred method of dealing with options in final argument hash iHiD 5/17/12 10:40 AM
Hi guys,

I'm wondering what the preferred method of parsing the "options" hash is?

In one file, I've just seen these three different methods:

def foobar(options = {})
  options.reverse_merge!(:length => 30)
  #...
  call_another_method(options[:length])
end

def foobar(options = {})
  options[:length] ||= 30
  #...  
  call_another_method(options[:length])
end

def foobar(options = {})
  length = options[:length] || 30
  #...
  call_another_method(length)
end

I'd like to go through and standardise them, at least in the files I'm working on. 

Which is the preferred method?

Thanks,
Jeremy
Re: [Rails-core] Preferred method of dealing with options in final argument hash Donald Ball 5/17/12 10:48 AM
I would strongly advocate using the Hash#fetch method in general:

options.fetch(:length, 30)

Though it's worth noting it gives different results than the || idiom
for nil and false hash values.

-- donald
Re: [Rails-core] Preferred method of dealing with options in final argument hash Jeremy Evans 5/17/12 11:09 AM
It also gives different results if options has a default value or a
default proc.

If the default value is expensive to produce, using the block version
of Hash#fetch may be better for performance, as then it will only
produce the expensive value if the options hash doesn't contain the
option.

It's generally considered bad style to modify arguments passed into a
method unless that is the purpose of the method itself.  Using:

  options.reverse_merge!(:length => 30)

or

  options[:length] ||= 30

modifies the options hash, and that's a bad idea IMO.

Jeremy