05 Mar 08 A better “try()” for Ruby, why not do the Groovy way?

The new method in Ruby 1.9 is making some people happy and creative too.
The only problem with that in my opinion is that every one is fixed about using method chaining with the name “try” with a symbol as a parameter to escape from the:

@person.name unless @person.nil?

or

@person ? @person.name : nil

and for some strange reason they think it is natural to write:

@person.try(:name)

when I see the sentence above, the first thing I want to “try” is:

@person.try(:to_swim)

Ok, the last comment was not cool, but I thought it would be funny

So, what is this post about?

In Groovy there is a built’in language construct to solve this situation in a very cool way:

person?.name

The method call after the “?” is only called if the previous expression was not nil.

I could not think in a way to implement any thing like that in ruby, but I think I came out with a satisfactory solution.
What do you think about flagging your method calls with “I know this can be null, but ignore it, it is a normal situation”?
No, I’m not telling you to write all this sentence in your code
the flag I’m using now is the “_” character.

I’m monkey patching ruby like this:

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class NilClass
   alias :old_method_missing :method_missing
   def method_missing(methodname,*args)
	  old_method_missing methodname, *args unless methodname.to_s =~ /.*_$/
   end
end
class Object
   alias :old_method_missing :method_missing
   def method_missing(methodname,*args)
      methodname = (methodname.to_s.gsub(/(.*)_$/,'\1')).to_sym
	  if respond_to? methodname
	     send methodname,*args
	  else
	     old_method_missing methodname, *args 
	  end
   end
end

and you can use it like this:

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#test classes
class Named
	attr_accessor :name
	def initialize(name)
		@name = name
	end
end
class Person < Named
	attr_accessor :name, :company
	def initialize(name,company=nil)
		super(name)
		@company = company
	end
end
#Testing starts here
def run_test
	puts @person.name_
	puts @person.company_.name_
end
@person = Person.new('Urubatan',Named.new('The Best'))
run_test
@person = nil
run_test

With this little method missing hack, we just put an “_” in the end of the method name we want to call and if the target object is nil the method will not be called and we will not get a NoMethodError.
Better yet, we can even pass arguments to the method we want to call

This way, we can use this solution only in situations we know it is safe.
What do you think about this?
I prefer the groovy solution, but I kine this one better than the “try” method

<updated>
Added one more link to the list in the beggining of the post (thanks coderr)
</updated>

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Tags: method_missing, monkeypatch, NoMethodError, ruby, try