Rails: How to find_by a field containing a certain string

I have a model named Topic, that has a name as a field.

So say I have a term I'm searching for, apple.

If I do a

Topic.find_by_name("apple")

I get a record back with the name apple. That's good -- but how do I change find_by_name so that it can find "apple juice" as well as "apple" -- basically, find names that contain the original query or exactly match the original query?

Edit: Thanks for all the response. I guess I should've been a little more clear earlier, but what if I want to find by a variable name (obviously I'm not going to want to find by the name "apple" everytime :) )?

How do I manipulate Topic.where to accommodate for this? So something like...

@topic = Topic.where(......., @name)

I think something like this should work:

Topic.where("name like ?", "%apple%")

To accomodate for your edit:

Topic.where("name like ?", "%#{@search}%")

Basic string interpolation, you're using the value of @search inside the string %%, so you @search = "apple" then you end up with %apple%

With PostgreSQL you can also use match operators:

Topic.where("name ~* ?", @search)

Looks like in Rails 3 you would want to use the where:

Topic.where("name ILIKE ?", "%apple%")

Don't put string directly like that. Its called SQL injection. You should instead use .where:

Topic.where("name like '?%' ", params[:name])

Try

Topic.where("name like ?",'%apple%')
Topic.find(:all, :conditions => ["name like ?","%apple%"])