init project

app/models/challenge_choose.rb

@@ -0,0 +1,9 @@
+class ChallengeChoose < ApplicationRecord
+  default_scope {order("challenge_chooses.position asc")}
+  belongs_to :challenge, optional: true
+  has_many :challenge_tags, :dependent => :destroy
+  has_many :challenge_questions, dependent: :destroy
+
+  validates :subject, length: { maximum: 25000, too_long: "不能超过25000个字符" }
+
+end