HABTMとhas_oneモデルエラー

Question

私は2つのクラス：RestreamとChannelを持っています。チャネルには多くの再ストリームがあり、再ストリームは多くのチャネルに属している可能性があります。しかし、Restreamにはactive_channel - これを使用しているチャンネルのIDも格納する必要があります。

class Restream < ActiveRecord::Base 
    has_one :active_channel, class_name: 'Channel' 

    has_and_belongs_to_many :channels 
    ... 
end 

class Channel < ActiveRecord::Base 
    has_and_belongs_to_many :restreams 
    ... 

end 

私が追加active_channelために書いたの移行：

add_column :restreams, :active_channel, :integer, index: true 
add_foreign_key :restreams, :channels, column: :active_channel 

それでも私はこれを取得、私はrails cを実行し、Restream.lastを呼び出すたび：

irb(main):002:0> Restream.last 
    Restream Load (1.2ms) SELECT "restreams".* FROM "restreams" ORDER BY "restreams"."id" DESC LIMIT 1 
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR: column channels.restream_id does not exist 
LINE 1: SELECT "channels".* FROM "channels" WHERE "channels"."restr... 
               ^
: SELECT "channels".* FROM "channels" WHERE "channels"."restream_id" = $1 ORDER BY "channels"."name" ASC LIMIT 1 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/connection_adapters/postgresql_adapter.rb:637:in `prepare' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/connection_adapters/postgresql_adapter.rb:637:in `prepare_statement' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/connection_adapters/postgresql_adapter.rb:596:in `exec_cache' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/connection_adapters/postgresql_adapter.rb:585:in `execute_and_clear' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:160:in `exec_query' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/connection_adapters/abstract/database_statements.rb:355:in `select' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/connection_adapters/abstract/database_statements.rb:32:in `select_all' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/connection_adapters/abstract/query_cache.rb:70:in `select_all' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/querying.rb:39:in `find_by_sql' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/relation.rb:639:in `exec_queries' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/association_relation.rb:32:in `exec_queries' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/relation.rb:515:in `load' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/relation.rb:243:in `to_a' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/associations/singular_association.rb:42:in `get_records' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/associations/singular_association.rb:57:in `find_target' 
    from /bundler_cache/gems/activerecord-4.2.5.1/lib/active_record/associations/association.rb:138:in `load_target' 
... 4 levels... 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/ext/active_record.rb:45:in `each' 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/ext/active_record.rb:45:in `inject' 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/ext/active_record.rb:45:in `awesome_active_record_instance' 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/formatter.rb:26:in `format' 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/inspector.rb:137:in `unnested' 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/inspector.rb:104:in `awesome' 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/core_ext/kernel.rb:10:in `ai' 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/core_ext/kernel.rb:20:in `ap' 
    from /bundler_cache/gems/awesome_print-1.6.1/lib/awesome_print/inspector.rb:31:in `output_value' 
    from /bundler_cache/gems/railties-4.2.5.1/lib/rails/commands/console.rb:110:in `start' 
    from /bundler_cache/gems/railties-4.2.5.1/lib/rails/commands/console.rb:9:in `start' 
    from /bundler_cache/gems/railties-4.2.5.1/lib/rails/commands/commands_tasks.rb:68:in `console' 
    from /bundler_cache/gems/railties-4.2.5.1/lib/rails/commands/commands_tasks.rb:39:in `run_command!' 
    from /bundler_cache/gems/railties-4.2.5.1/lib/rails/commands.rb:17:in `<top (required)>' 
    from bin/rails:4:in `require' 
    from bin/rails:4:in `<main>' 

が、私はそれは声明で失敗していること、が分かりましたSELECT "channels".* FROM "channels" WHERE "channels"."restream_id" = $1 ORDER BY "channels"."name" ASC LIMIT 1

私は何ですか間違っている？ Thanx

Answer 1

ここでの問題は、列名がrestream_idではなく、restreamsであることです。

そして、あなたはChannelためRestreamに列と外国の参照を追加しましたが、1はChannelがあなたのコードから他の方法で回避されている、Restreamに属することを意味しているという。

RestreamはChannelに属していると簡単に言えます。

class Restream < ActiveRecord::Base 
    belongs_to :active_channel, class_name: 'Channel' 
    has_and_belongs_to_many :channels 
    ... 
end 

class Channel < ActiveRecord::Base 
    has_and_belongs_to_many :restreams 
    ... 
end 

このソリューションは、「アクティブな」チャネルをリストライムに保存することを前提としています。つまり、1つのチャネルに複数の/ 1つのリストリームを含めることができます。

逆の場合は、すべてのコードを切り替えて、DBをロールバックして移行を行う必要があります。すべてが機能するはずです。

Answer 2

あなたは列名を混乱させました。 ActiveRecordの規則では、外部キー列は_idで終わる必要があります。

不適切な移行をまだコミットしていない場合は、単にrake db:rollbackでロールバックして移行を修正することができます。

add_column :restreams, :active_channel_id, :integer, index: true 
add_foreign_key :restreams, :channels, column: :active_channel_id 

それ以外の場合は、列の名前を変更する新しい移行を作成する必要があります。

remove_foreign_key(:restreams, :channels, column: :active_channel) 
remove_index(:restreams, :active_channel_id) 
rename_column(:restreams, :active_channel, :active_channel_id) 
add_foreign_key(:restreams, :channels, column: :active_channel_id) 
add_index(:restreams, :active_channel_id) 

、後者は関係の反対側に外部キー列を置くと、あなたがbelongs_toなくhas_one関係を使用する必要があります。

class Restream < ActiveRecord::Base 
    # stores the relation as `restreams.active_channel_id` 
    belongs_to :active_channel, class_name: 'Channel', 
           optional: true 

    has_and_belongs_to_many :channels 
    ... 
end 

class Channel < ActiveRecord::Base 
    # or has_one 
    has_many :active_restreams, class_name: 'Restream', 
           foreign_key: 'active_channel_id' 
    has_and_belongs_to_many :restreams 
    ... 

end