问题
I have a where operation on a model that returns a single object. But I can't seem to use it in object notation (it appears to return an array with the object at [0]).
store = Store.where("some_id = ?", some_id)
puts store.name # doesn't work
puts store # shows array with the object at [0]
回答1:
Because sometimes you don't know how many objects a query should return, so for consistency you always get an array.
To get a single object use
store = Store.where("some_id = ?", some_id).first
If you are looking for the primary ID of the model, you can also use
store = Store.find(some_id)
which will raise a RecrodNotFound exception (handled by rails as a 404 by default) if it doesn't find the object.
回答2:
There are also dynamic finders
Store.find_by_some_id(some_id)
They are equivalent to
Store.where(:some_id => some_id).first
回答3:
Where clause in rails 3.x will always return and arel objec, which you can use for method chaining.
Thus return statement of the where clause is always an array.
For accessing the first element you have to do
object.first as suggested by Jakub
来源：https://stackoverflow.com/questions/8026095/why-does-a-single-record-lookup-return-an-array-rails-beginner