w3d3 rails Flashcards
How do you run migrations
bundle exec rails db:migrate
How do you create a database with rails
set up config/database.yml
bundle exec rails db:create
What are 5 gems to add to rails for development
annotate better_errors binding_of_caller byebug pry-rails
How do you run migrations?
rails db:migrate
Where can you see a copy of your database’s current schema as reported by rails?
db/schema.rb
What’s the best/fastest way to initialize a new database? What does this rely on?
rails db:schema:load
db/schema.rb
How do you enforce that a column must have a value?
within create_table:
t.string :name, null: false
What’s the difference between belongs_to and has_many ?
What do they have in common?
belongs_to exists on the model that contains the primary key
has_many exists on the other model
They allow the use of helper instance methods
What arguments are passed to a belongs_to or has_many association?
(trick) answer: two
better answer: we use ruby’s ability to use a hash as a final argument without braces to pass several options to the association method like so:
belongs_to :table_name, primary_key: :id,
foreign_key: :foreign_key_id,
class_name: ‘SomeClass’
example:
belongs_to :house,
brimary_key: :id,
foreign_key: :house_id,
class_name: ‘House’
What arguments are passed to a belongs_to or has_many association?
(trick) answer: two
better answer: we use ruby’s ability to use a hash as a final argument without braces to pass several options to the association method like so:
belongs_to :table_name, primary_key: :id,
foreign_key: :foreign_key_id,
class_name: ‘SomeClass’
example:
belongs_to :house,
brimary_key: :id,
foreign_key: :house_id,
class_name: ‘House’
What does this do:
validates :attribute, presence: true
It validates that a particular attribute exists on a method when we call #save
How do we validate the uniqueness of an attribute for an object?
Add this to a validates macro:
uniqueness: true
How do we create a custom validator for a model?
- create a method that conditionally shovels an error message into a new key on the self.errors hash
- add this line:
validate :my_validator_method_name
How do we see the errors for an object?
errors.full_messages
What’s the difference between ApplicationModel#save and #save!
save will return false if there are errors.
What’s the difference between ApplicationModel#save and #save!
save will return false if there are errors.
How would you use a symbol as a value in a SQL string?
awesome_symbol: 55
<
What are two levels of data integrity-protection in rails?
DB-level constraints
Model-level validations
Why shouldn’t you roll back a migration?
Can make things out-of-sync with other people working on the same database.
Impossible to keep consistent with a production database.
How do you get to a sql console in rails?
rails db
What is the superclass for all rails models?
ApplicationRecord
What is ApplicationRecord
The superclass that all rails models inherit from.
When does code directly inside a class definition run?
When the class is first parsed.
How do you recreate your db from scratch? What steps does this take?
rails db:reset
- drops entire database
- runs db:migrate
- runs db:seed
