Person.find_or_create_by(name: 'Spartacus', rating: 4) # returns the first item or returns a new instance (requires you call. Person.find_or_initialize_by(name: 'Spartacus', rating: 4) Person.find_by(name: 'Spartacus', rating: 4) # returns a chainable list (which can be empty). Variations of find Person.where(name: 'Spartacus', rating: 4) By locking the row, the second transaction has to wait until the first is finished we get the expected person.visits = 4. Find with lockĮxample for find with a lock: Imagine two concurrent transactions: each will read person.visits = 2, add 1 to it, and save, resulting in two saves of person.visits = 3. But ActiveRecord::QueryMethods#where method doesn't raise ActiveRecord::RecordNotFound. If you want the results to be sorted by database, you can use ActiveRecord::QueryMethods#where method and provide an explicit ActiveRecord::QueryMethods#order option. NOTE: The returned records are in the same order as the ids you provide. Person.where("administrator = 1").order("created_on DESC").find(1) Person.find() # returns an array for the object with ID = 1 Person.find() # returns an array for objects with IDs in (7, 17) Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6) Person.find("31-sarah") # returns the object for ID = 31 Person.find("1") # returns the object for ID = 1 Person.find(1) # returns the object for ID = 1 If the primary key is an integer, find by id coerces its arguments by using to_i. If one or more records cannot be found for the requested ids, then ActiveRecord::RecordNotFound will be raised. Person.where(name: 'Spartacus', rating: 4).exists?įind by id - This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids (). String - Finds the record with a primary key corresponding to this string (such as '5').Īrray - Finds the record that matches these where-style conditions (such as ) Integer - Finds the record with this primary key. Returns true if a record exists in the table that matches the id or conditions given, or false otherwise. Since the database exists already, we don’t need the migration file. Rails generate scaffold Article title:string body:text Step 9 : Delete the Articles Migration file Open your terminal and run the following command : Repeat steps 5 and 6 Step 8 : Generate The CRUD for Articles The final SQL Command to create the table should look like this : CREATE TABLE articles ( id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY, title VARCHAR(50), body TEXT, created_at DATETIME DEFAULT NULL, updated_at DATETIME DEFAULT NULL ) To fix this, tweak the articles table structure a bit. Of course there is a tiny mistake here ! Following rails conventions, the fields created_at updated_at are handled by default and should not be included in the fields list of the scaffold command. (copied to your clipboard) Step 7: Update table structure to follow Rails Conventions Rails generate scaffold Article title:string body:text created:datetime modified:datetime Options are: 4 for table 4 (4.6) for table 4 to 6 for tables 4 and 6 * for all Tables Scaffold -c -p ~/path_to_rails_app/db/schema.rb It’s time now to make use of the gem we previously installed Rails db:schema:dump Step 6: Generate the scaffold commands The next step is to generate the schema.rb file based on the existing db More info on the gem here Step 5 : Generate the schema Now, we need to install the gem that will do the work for us : Sudo apt-get install xclip Step 4: Install the required gem if you are using a Debian based distro like me, execute: Grab it from the repo of your linux distribution. Ĭreate the table articles with the following SQL Command : CREATE TABLE articles ( id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY, title VARCHAR(50), body TEXT, created DATETIME DEFAULT NULL, modified DATETIME DEFAULT NULL ) Step 3 : Install xclip Now we link our freshly rails app to our existing db by tinkering database.ymlĭefault: &default adapter: mysql2 encoding: utf8 pool: 5 username: password: socket: /var/run/mysqld/mysqld.sockįor the purpose of this tutorial we will work on a db called blog with one table called articles. Rails new -d mysql Step 2: Configure the database Let’s start! STEP 1: Create a rails project If you are maintaining a legacy app or planning to migrate from another technology to Rails anyway, it can be daunting if you don’t pay attention to the conventions that the Rails framework impose. If done right, the migration will be worth it How to build a Rails app on top of an existing database
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