conditional chaining in ruby

Question

Is there a good way to chain methods conditionally in Ruby?

What I want to do functionally is

if a && b && c
 my_object.some_method_b         


        

Answer 1

Although the inject method is perfectly valid, that kind of Enumerable use does confuse people and suffers from the limitation of not being able to pass arbitrary parameters.

A pattern like this may be better for this application:

object = my_object

if (a)
  object = object.method_a(:arg_a)
end

if (b)
  object = object.method_b
end

if (c)
  object = object.method_c('arg_c1', 'arg_c2')
end

I've found this to be useful when using named scopes. For instance:

scope = Person

if (params[:filter_by_age])
  scope = scope.in_age_group(params[:filter_by_age])
end

if (params[:country])
  scope = scope.in_country(params[:country])
end

# Usually a will_paginate-type call is made here, too
@people = scope.all