DataMapper: Create new record or update existing

问题

Does DataMapper provide a convenient way to create a new record when none exists or update an existing one? I couldn't find anything in the API documentation.

This is what I have at the moment which doesn't seem very elegant:

foo = Foo.get(id)
if foo.nil?
  foo = Foo.create(#attributes...)
else
  foo.update(#attributes...)
end
foo.save

回答1:

Foo.first_or_create(:id=>id).update(attributes)

or

(Foo.get(id) || Foo.new).update(attributes)

回答2:

I just try

Foo.first_or_create(:id=>id).update(attributes)

but it gets wrong sometimes, so I find some tips from here:DataMapper Docs

Now I make my code works like:

Foo.first_or_create({:id=>id}, {:name => name}).update(:id => id, :name => name)

Hope it helps you.

来源：https://stackoverflow.com/questions/2567686/datamapper-create-new-record-or-update-existing