Chapter 6

Question 0

What is the syntax to generate a model?

Answer 0

$rails generate model singularModelName attribute1:datatype attribute2:datatype

Question 1

What is the default Rails library used for interacting with a database?

Answer 1

ActiveRecord

Question 2

What is the difference between model names and controller names?

Answer 2

Controller names are plural

Question 3

What is a migration?

Answer 3

A way to alter the structure of a database incrementally, so that models can adapt to changing requirements

Question 4

How do we run the scripts to ‘migrate up’ our database?

Answer 4

$bundle exec rake db:migrate

Question 5

What is the name of the column Rails generates in the database for each row?

Answer 5

ID; an integer

Question 7

How do we ‘migrate down’ and undo a database migration?

Answer 7

$bundle exec rake db:rollback

Question 8

What is the command to start the rails console in a way that any changes to the database are rolled back upon exiting the console?

Answer 8

$rails console –sandbox

Question 9

What is the command to insert a new object into the database?

Answer 9

newObject.save

This method returns a boolean of whether or not it was successful

Question 10

T/F: an model object created with #new is not saved to the database.

Answer 10

T; It is added to the database with #save

Question 11

What is special about the model method #create

Answer 11

It makes a new instance of the model and updates the database accordingly, and returns the object

Question 12

What is the inverse of #create

Answer 12

destroy

Question 13

What are the Active Record methods to find users?

Answer 13

find, which takes an id integer

Question 14

If we have made changes to an object but have not saved these changes to a database and want to roll back to the values in the database, what method is used?

Answer 14

instance.reload.attributeName

Question 15

What is a method to update multiple attributes?

Answer 15

update_attributes(options hash)

Question 16

What is an Active Record validation?

Answer 16

It ensures that any addition/modification to the database conforms to certain rules

Question 17

What is the syntax of the ‘validates’ function?

Answer 17

validates(attribute, options hash)

Question 18

How can we see the errors produced when an object fails a validation?

Answer 18

objectName.errors.full_messages

Question 19

What is the method to see if an object passes all validations?

Answer 19

valid?

Question 20

Explain the following regex:

/\A[\w+-.]+@[a-z\d-.]+.[a-z]+\z/i

Answer 20

From the start of the string (\A), find at least one character, plus, hyphen, or dot ([\w+-.]), followed by (+) the literal @ sign, followed by at least one letter, digit, hyphen, or dot ([a-z\d-.]), followed by a literal dot, followed by at least one letter ([a-z]), followed by an end of the string (\z)

Question 21

T/F: The ‘uniqueness’ option for the validates function looks in the database to see if the record in question exists

Answer 21

T