I simply want to group cities by their state and from there have the array of the hash key (ie State Name ) return an array of hash data pertaining to it's cities. Right now I have something like this:
City.all.group_by { |c| c.state.name }
Which will return:
{
"Illinois": [# < City id: 3, name: "Chicago", state_id: 3 > ],
"Texas": [# < City id: 2, name: "Houston", state_id: 2 > ],
"California": [# < City id: 1, name: "Los Angeles", state_id: 1 > ],
"New York": [# < City id: 4, name: "New York City", state_id: 4 > ]
}
Notice how it returns an array of rails objects. Instead I want to return an array of hashes with certain attributes, like their id
and name
.
The reason the grouped values are Rails objects (your models) is due to the fact that you also start with these objects. You can use the attributes
method to retrieve the attributes of a model instance as a hash.
The following achieves the result you want:
City.all.group_by { |city| city.state.name }
.transform_values { |cities| cities.map(&:attributes) }
If you only want specific attributes, use slice
instead:
City.all.group_by { |city| city.state.name }
.transform_values { |cities| cities.map { |city| city.slice(:id, :name) } }
Note that slice
will return an ActiveSupport::HashWithIndifferentAccess
instance. Which mostly can be used in the same manner as a normal hash, but returns the same value for both hash[:name]
and hash['name']
. If you rather use a normal hash append a to_hash
call after the slice
call.
This should be enough for you
City.all.group_by { |c| c.state.name }.map {|k,v| [k, v.attributes] }.to_h
and to select only specified attributes do
v.attributes.slice(:name, :id)
One of the easiest approach is to convert it into json object
City.all.as_json.group_by { |c| c.state.name }
this will fix the issue
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