Filtering in Ruby on Rails - ruby-on-rails

Question

I have an Ruby on Rails application in which I have the following resources pets, pet types, vaccinations(the event of vaccinating a pet) and persons. So, pet belongs to a type (a type has many pets) and vaccination belongs to a pet (a pet can have many vaccinations). What I want to do is the following: To have a collapsable list (a select) o all the pet types with a submit button in the vaccinations index, so that I can filter vaccinations by pet types. My code is the following:
This is the index method in the vaccination controler:
def index
if params[:type_id]
flash[:notice] = "Post successfully created"
#vaccinations = Vaccination.filter(params[:type_id])
else
#vaccinations = Vaccination.all
end
end
This is the search form in the vaccinations index:
<form action="/vaccinations" method="GET">
<%= #type_id %>
<select name="type_id">
<option disabled selected value> Select a classification </option>
<% Type.all.each_with_index do | t, index | %>
<option value="<%= t.id %>" <% t.id.to_s == #type_id ? "selected" : "" %>> <%= t.name%> </option>
<% end -%>
</select>
<input type="submit", value="SUBMIT" />
</form>
And this is my filter method in the vaccination model, the one that I call in the controller.
def self.filter(type_id)
t = Array.new
for v in Vaccination.all
if type_id == v.pet.type.id
t.push(v)
end
end
t
end
What happens is that when I don´t select any pet type, I can see every vaccination as it should be. But when I select any pet type, no matter the type of the pets that have been through a vaccination, it doesn´t show me anything. If i have made three vaccinations to cats an select cat, and filter, it shows me nothing as if I didn´t have any vaccinations. That´s my problem. Sorry for my english, it´s not my first language!

Answer 1

The correct way of doing it is through relationships.
Example ( should work fine, didn't test it ):
def self.filter(type_id)
Vaccination.joins(pet: :pet_type).where(
pet_types: {
id: type_id
}
)
end
Now you will get a list of vaccinations of all the pets with the sent type.