ERD on Rails 68th RubyKansai Takashi Ogomori 

ERD on Rails Rails͸Active RecordͰϞσϧΛૢ࡞Λ͢Δɻ Ϟσϧʹ͸ΞιγΤʔγϣϯΛઃఆͰ͖Δɻ 2/10 

Example Domain ֓ཁʢՁ஋ʣ Ϣʔεέʔε ΦϒδΣΫτ ߦࣄ؅ཧγεςϜʢΠϕϯτΛ։࠵ͯ͠ɺίϛϡχςΟΛߏஙʣ · ར༻ऀ͸ίϛϡχςΟΛ૑ઃͰ͖Δɻ ར༻ऀ͸ίϛϡχςΟʹೖձͰ͖Δɻ ίϛϡχςΟʹೖձ͢ΔͱϝϯόʔʹͳΔɻ ίϛϡχςΟ͸ΠϕϯτΛ։࠵Ͱ͖Δɻ Πϕϯτ͸νέοτΛൃߦͰ͖Δɻ ϝϯόʔ͸νέοτೖखͰ͖Δɻ · · · · · · ར༻ऀ, ίϛϡχςΟ, ϝϯόʔ, Πϕϯτ, νέοτ · 3/10 

Associations One-to-manyʢ1ରଟʣ Many-to-manyʢଟରଟʣ One-to-Oneʢ1ର1ʣ ̍ͭͷίϛϡχςΟ͸ଟ਺ͷΠϕϯτΛ։࠵Ͱ͖Δɻ ̍ͭͷΠϕϯτ͸ଟ਺ͷνέοτΛൃߦ͢Δ͜ͱ͕Ͱ͖Δɻ · · ར༻ऀ͸ଟ਺ͷίϛϡχςΟʹՃೖ͢Δ͜ͱ͕Ͱ͖Δɻ ϝϯόʔ͸ෳ਺ͷΠϕϯτʹࢀՃͰ͖Δɻ · ίϛϡχςΟ͸ଟ਺ͷར༻ऀΛՃೖͤ͞Δ͜ͱ͕Ͱ͖Δɻ - · Πϕϯτ͸ෳ਺ͷϝϯόʔΛࢀՃͤ͞Δ͜ͱ͕Ͱ͖Δɻ - ̍ͭͷίϛϡχςΟ̍ͭͷϙϦγʔΛ࣋ͭ͜ͱ͕Ͱ͖Δɻ · 4/10 

Domain Specific Language (DSL) Types આ໌ belongs_to ࢀর has_one ͻͱ͚ͭͩ࣋ͭ has_many ෳ਺࣋ͭ has_many through ... Λ௨ͯ͡ෳ਺࣋ͭ has_one through ... Λ௨ͯ͡ͻͱ͚ͭͩ࣋ͭ has_and_belongs_to_many ࢀরͱෳ਺࣋ͭ 5/10 

Generate 1 One-to-manyʢ1ରଟʣ One-to-Oneʢ1ର1ʣ $ rails generate scaffold group name $ rails generate scaffold event group:references has_many :events belongs_to :group $ rails generate scaffold policy group:references has_one :policy 6/10 

Generate 2 Many-to-manyʢଟରଟʣ Many-to-manyʢଟରଟʣ $ rails generate scaffold user name $ rails generate scaffold member user:references group:references has_many :members has_many :groups, through: :members has_many :users, through: :members $ rails generate scaffold ticket event:references member:references has_many :tickets has_many :events, through: :tickets has_many :members, through: :tickets 7/10 

Generate 3 PolymorphicʢϙϦϞʔϑΟοΫʣ $ rails generate scaffold image imageable:references{polymorphic} name has_many :images, as: :imageable 8/10 

ERD 9/10 

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