Rails 4活动记录循环依赖性错误

These are my tables:

这些是我的表：

create_table :messages do |t|
  t.integer :type
  t.string :text
  t.datetime :sent_date
  t.string :sender
  t.timestamps
end

create_table :users do |t|
  t.integer :phone
  t.string :fullname
  t.string :profile_image
  t.timestamps
end

create_table :send_tos do |t|
  t.string :receiver
  t.belongs_to :message
  t.boolean :is_received
end
create_table :