Preferred method of dealing with options in final argument hash

rubyonrails-core
1

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

2

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

3

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