Conditions with Bind Variables and Optional Parameters - ruby-on-rails

Question

Let's say I have a form where users can search for people whose name starts with a particular name string, for example, "Mi" would find "Mike" and "Miguel". I would probably create a find statement like so:
find(:all, :conditions => ['name LIKE ?', "#{name}%"])
Let's say the form also has two optional fields, hair_color and eye_color that can be used to further filter the results. Ignoring the name portion of the query, a find statement for people that can take in an arbitrary number of optional parameters might look like this:
find(:all, :conditions => { params[:person] })
Which for my two optional parameters would behave as the equivalent of this:
find(:all, :conditions => { :hair_color => hair_color, :eye_color => eye_color })
What I can't figure out is how to merge these two kinds of queries where the required field, "name" is applied to the "like" condition above, and the optional hair_color and eye_color parameters (and perhaps others) can be added to further filter the results.
I certainly can build up a query string to do this, but I feel there must be a "rails way" that is more elegant. How can I merge mandatory bind parameters with optional parameters?

Answer 1

This is the perfect use of a named scope.
create a named scope in the model:
named_scope :with_name_like, lambda {|name|
{:conditions => ['name LIKE ?', "#{name}%"]}
}
At this point you can call
Model.with_name_like("Mi").find(:all, :conditions => params[:person])
And Rails will merge the queries for you.
Edit: Code for Waseem:
If the name is optional you could either omit the named scope from your method chain with an if condition:
unless name.blank?
Model.with_name_like("Mi").find(:all, :conditions => params[:person])
else
Model.find(:all, :conditions => params[:person])
end
Or you could redefine the named scope to do the same thing.
named_scope :with_name_like, lambda {|name|
if name.blank?
{}
else
{:conditions => ['name LIKE ?', "#{name}%"]}
end
}
Update
Here is the Rails 3 version of the last code snippet:
scope :with_name_like, lambda {|name|
if not name.blank?
where('name LIKE ?', "#{name}%")
end
}

Answer 2

To comply also with Waseem request, but allowing nil instead blank? (which is udeful in case you want to use "#things = Thing.named_like(params[:name])" directly)
named_scope :named_like, lambda do |*args|
if (name=args.first)
{:conditions => ["name like ?",name]}
else
{}
end
end
# or oneliner version:
named_scope :named_like, lambda{|*args| (name=args.first ? {:conditions => ["name like ?",name]} : {}) } }
I hope it helps