importing csv into ruby but need to create relationship

Question

I am wanting to import 2 files (County & State). When I import I need to create a relationship with County to State.

My State CSV file has:

id
state e.g. "Connecticut"
abbreviation e.g. "CT"

My County CSV file has:

id
name e.g. "Hartford"
market_state e.g. "Connecticut"

The attributes for MarketCounty are:

create_table "market_counties", force: :cascade do |t|
  t.string   "name"
  t.integer  "market_state_id"
  t.datetime "created_at",      null: false
  t.datetime "updated_at",      null: false
end

The attributes for MarketState are:

create_table "market_states", force: :cascade do |t|
  t.string   "name"
  t.string   "abbreviation"
  t.datetime "created_at",   null: false
  t.datetime "updated_at",   null: false
end

My models have these relationships:

MarketState:

class MarketState < ActiveRecord::Base
  has_many :market_reports, as: :location
  has_many :market_cities
  has_many :market_zips
  has_many :market_counties  
end

MarketCounty:

class MarketCounty < ActiveRecord::Base
  has_many :market_reports, as: :location
  has_many :market_cities
  has_many :market_zips
  belongs_to :market_state
end

My Rake task:

def import_market_states
  MarketState.create!(name: "Connecticut", abbreviation: "CT")
end

def import_market_counties
  path = Rails.root.join("config/csv/locations/counties.csv")
  CSV.foreach(path, headers: true) do |row|
    MarketCounty.create! row.to_hash
  end

My question is in the the method import_market_counties, row.to_hash does not work.

ActiveRecord::AssociationTypeMismatch: MarketState(#70157557268540)
expected, got String(#70157439770720)

I set it up manually:

MarketCity.create!(name: "Hartford", market_state: MarketState.find_by(abbreviation: "CT")

How can I do a "lookup" in a loop when importing County file (to associate it to the MarketState model)?

To clarify, the issue is that when I am creating the County, I am not trying to populate state with CT. I need to populate state_id with the association.

I found this SO: When importing a CSV, how do I handle data in a row that corresponds to an association? --- And thinking it may be similar to what I am trying to do - just not sure how to apply it here.

Please edit your question to include an example of the data you're working with. You said "row.to_hash does not work" but you forgot to say what row looks like. — Jordan Running
– Jordan Running, Commented Jun 8, 2016 at 16:46
What is in a row of the config/csv/locations/counties.csv file? — ruby_newbie
– ruby_newbie, Commented Jun 8, 2016 at 16:57
see above: My County csv file has id: name: Hartford market_state: Connecticut — user2970050
– user2970050, Commented Jun 8, 2016 at 17:00
Do you want to use the id field from the CSV as the models' id attribute or do you want those to be automatically generated by your database? (Unless you know there will never be conflicts with data already in the database, the latter is safer, but if the id field is significant in some other way you may not want to lose it.) — Jordan Running
– Jordan Running, Commented Jun 8, 2016 at 17:33

ruby_newbie · Accepted Answer · 2016-06-08 17:08:03Z

1

Assuming your MarketState has a name column that is the name of the state:

def import_market_counties


path = Rails.root.join("config/csv/locations/counties.csv")
  CSV.foreach(path, headers: true) do |row|
    MarketState.find_by_name( row['market_state'].strip )
  end

you can also use find_or_create_by if you want to create the state if it doesn't exist.

answered Jun 8, 2016 at 17:08

ruby_newbie

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1 Comment

user2970050 Over a year ago

but then how to i populate the County field (market_state_id) which is the association on the County field?

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