[英]Rails 4 scope on HABTM association
I'm a rails newbie and I created a scope on a HABTM association, but I still think it looks unnatural, not elegant, so I think there must be a better way of doing it. 我是一个铁杆新手,我在HABTM协会上创建了一个范围,但我仍然认为它看起来不自然,不优雅,所以我认为必须有一个更好的方法。 Could anyone advise me if there is such better way? 任何人都可以告诉我,如果有更好的方法吗? I've seen other posts where people have the same question ( Scope for Self-joining HABTM Association ) with no answer... 我见过其他帖子,人们有同样的问题( 自我加入HABTM协会的范围 )没有回答......
class User < ActiveRecord::Base
has_and_belongs_to_many :roles, :join_table => :users_roles
end
class Role < ActiveRecord::Base
has_and_belongs_to_many :users, :join_table => :users_roles
end
scope :by_role, lambda { |role_name| joins('join users_roles on users.id = users_roles.user_id').
joins('join roles on users_roles.role_id = roles.id').
where('roles.name = ?', role_name) }
try this. 尝试这个。 it is more optimized. 它更加优化。
scope :by_role, ->(role) { joins(:roles).where(roles: { name: role }) }
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