The summary line again is relationship :trails, :summary => :list, :fields => [:name, :difficulty].

总结行还是relationship :trails, :summary => :list, :fields => [:name, :difficulty]。

youdao

The summary line again is relationship :trails, :summary => :list, :fields => [:name, :difficulty].

总结行还是relationship :trails, :summary => :list, :fields => [:name, :difficulty]。

youdao