HABTM 重复记录 [英] HABTM duplicate records

问题描述

我有 2 个模型 Game &Theme 并且它们有一个 has_and_belongs_to_many 关联.我尝试了许多解决方案来防止 games_themes 表中的重复记录，但没有任何解决方案有效.问题是，games_themes 是一个表格，但它不是一个模型，所以我无法找到一种有效地对其进行验证的方法.

I have a 2 models Game & Theme and they have a has_and_belongs_to_many association. I have tried many solutions to prevent duplicate records in the games_themes table, but no solutions work. The problem is, games_themes is a table, but it is not a model, so I can't figure out a way to run validations on it effectively.

这是我尝试过的解决方案

Heres a solution I tried

class Theme < ActiveRecord::Base
  has_and_belongs_to_many :games, :uniq => true
end

class Game < ActiveRecord::Base
  has_and_belongs_to_many :themes, :uniq => true
end

推荐答案

您应该使用数据库级验证:

You should use database-level validation:

#new_migration
add_index :games_themes, [:game_id, :theme_id], :unique => true

<小时>

HABTM

这将防止您在数据库中保存任何重复数据.减轻 Rails & 的负担确保您只有游戏或主题.问题是因为 HABTM 没有模型，所以您无法在 Rails 中执行验证，这意味着您需要将其设为 db 级别

This will prevent you saving any duplicate data in the database. Takes the burden off Rails & ensures you only have game or theme. The problem is because HABTM doesn't have a model, there's no validation you can perform in Rails, meaning you need to make it db-level

正如评论中提到的，这意味着您必须像这样处理从数据库引发的异常:

As mentioned in the comments, this means you'll have to handle the exceptions raised from the db like this:

#app/controllers/games_controller.rb
def create
    #creation stuff here
    if @game.save
        #successful save
    else
        #capture errors
    end
end

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