How to add a pseudonymization and a search function? - ruby-on-rails

Question

I'm new to Ruby on Rails and I got two problems where I need some help:
I got the tables "cases" and "users". The table case includes the column "first name" and "last name". Now I want to add a unique string (pseudonymization) to each case for a special kind of identification without using the ID. This string should be build from the third letter of the first name and the total amount of letters plus the third letter of the last name and again the total amount of letters of the last name. E.g. for the name "Bill Smith" the string would be: L4I5.
Now the "users" should be able to find a specific case using that created special string. There should be a kind of a searching field where they can type in the string and click on search. Then the case with all the parameters should be shown.
What is the best way, to implement these two functions/features? I'm using rails 6.0.3.4 and ruby 2.7.0.
For better understanding see my schema.rb below.
ActiveRecord::Schema.define(version: 2021_01_28_100706) do
create_table "cases", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", force: :cascade do |t|
t.string "first_name"
t.string "last_name"
t.string "gender"
t.date "birthdate"
t.string "place_of_residence"
t.string "diagnosis"
t.bigint "user_id"
t.datetime "confirmed_at"
t.datetime "created_at", precision: 6
t.datetime "updated_at", precision: 6, null: false
t.bigint "diagnosis_id"
t.bigint "district_id"
t.bigint "report_id"
t.index ["diagnosis_id"], name: "index_cases_on_diagnosis_id"
t.index ["district_id"], name: "index_cases_on_district_id"
t.index ["report_id"], name: "index_cases_on_report_id"
t.index ["user_id"], name: "index_cases_on_user_id"
end
create_table "diagnoses", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", force: :cascade do |t|
t.string "illness"
t.datetime "created_at", precision: 6, null: false
t.datetime "updated_at", precision: 6, null: false
end
create_table "districts", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", force: :cascade do |t|
t.string "name"
t.string "place"
t.integer "postal_code"
t.datetime "created_at", precision: 6, null: false
t.datetime "updated_at", precision: 6, null: false
t.bigint "state_id", null: false
t.index ["state_id"], name: "index_districts_on_state_id"
end
create_table "reports", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", force: :cascade do |t|
t.bigint "district_id"
t.text "comment"
t.datetime "date"
t.bigint "user_id"
t.datetime "created_at", precision: 6, null: false
t.datetime "updated_at", precision: 6, null: false
t.index ["district_id"], name: "index_reports_on_district_id"
t.index ["user_id"], name: "index_reports_on_user_id"
end
create_table "states", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", force: :cascade do |t|
t.string "titel"
t.string "abbr"
t.datetime "created_at", precision: 6, null: false
t.datetime "updated_at", precision: 6, null: false
end
create_table "users", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", force: :cascade do |t|
t.string "email", default: "", null: false
t.string "encrypted_password", default: "", null: false
t.string "reset_password_token"
t.datetime "reset_password_sent_at"
t.datetime "remember_created_at"
t.datetime "created_at", precision: 6, null: false
t.datetime "updated_at", precision: 6, null: false
t.integer "role"
t.string "first_name"
t.string "last_name"
t.bigint "district_id"
t.bigint "state_id"
t.index ["district_id"], name: "index_users_on_district_id"
t.index ["email"], name: "index_users_on_email", unique: true
t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
t.index ["state_id"], name: "index_users_on_state_id"
end
end

Answer 1

You could add a column to the case table and a callback in the model to set it how you want. And to search just add a scope
#migration
add_column :cases, :new_column, :string, index: true
#model
class Case < ApplicationRecord
before_create :set_new_column
scope :by_new_column, ->(term) { where('new_column = ?', term) }
...
private
def set_new_column
self.new_column = "#{first_name[0]}#{last_name.length}"
end
end
Then in your controller or where ever, you could use like:
Case.by_new_column("C5")