mysql - Rails associations multiple string foreign key -

i can't seem figure out how match more 1 string column foreign key. have 2 models. shop , neighborhood. both have city , state column.

how can set association multiple foreign key string? right neighborhood of vancouver, bc show shops vancouver, bc , vancouver, wa.

shop - id - city (string) - state (string) - country (string)  belongs_to :neighborhood, foreign_key: :city, primary_key: :city  neighborhood - id - city (string) - state (string) - country (string)  has_many :shops, foreign_key: :city, primary_key: :city 

your pattern improved.

you're referencing "foreign_key" string... should integer. if refactor pattern, issue go away completely...

#app/models/shop.rb class shop < activerecord::base    # id | city_id | ...    belongs_to :city end  #app/models/city.rb class city < activerecord::base    has_many :shops    belongs_to :state #-> can removed end  #app/models/state.rb class state < activerecord::base    belongs_to :country #-> can removed end 

by nature, foreign_key has identify primary_key (unique_key) of associative table:

in context of relational databases, foreign key field (or collection of fields) in 1 table uniquely identifies row of table

this means if you're referencing city, should not matter if "name" of city same... if other table contains appropriate data (ie city uniquely located within state etc).

--

i recommend refactoring models shop belongs_to city. you'd able associate each city respective states etc.

instead of including state & country model, use countries gem, includes references various countries in world, , states.