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由 Jon Leighton 提交于
The previous implementation was necessary in order to support stuff like: class Post < ActiveRecord::Base default_scope where(published: true) scope :ordered, order("created_at") end If we didn't evaluate the default scope at the last possible moment before sending the SQL to the database, it would become impossible to do: Post.unscoped.ordered This is because the default scope would already be bound up in the "ordered" scope, and therefore wouldn't be removed by the "Post.unscoped" part. In 4.0, we have deprecated all "eager" forms of scopes. So now you must write: class Post < ActiveRecord::Base default_scope { where(published: true) } scope :ordered, -> { order("created_at") } end This prevents the default scope getting bound up inside the "ordered" scope, which means we can now have a simpler/better/more natural implementation of default scoping. A knock on effect is that some things that didn't work properly now do. For example it was previously impossible to use #except to remove a part of the default scope, since the default scope was evaluated after the call to #except.
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