Basic Ruby Commands

Question 0

How do you access the method new for the class Post?

Answer 0

Post.new

Question 1

What command opens an interactive Ruby session?

Answer 1

There is more than one, you can use the standard interactive ruby irb command, or you can use pry. You can also use rails console to open an irb session.

Question 2

How do you define a new method?

Answer 2

def sum(var1, var2)

** var1 + var2**

end

Question 3

How do you write a symbol in ruby?

Answer 3

:var

Question 4

Specify three debugging methods that will show you the fields of an object.

Answer 4

**<%= debug @objname %> **This will give you a formatted string using the yaml method.

**<%= simple_format @objname.to_yaml %> **Essentially the same as above.

<%= [1, 2, 3].inspect %> This will return unformatted text, but is useful for inspecting arrays.

Question 5

Name three different methods for debugging a Ruby on Rails app.

Answer 5

1. Debugging methods such as debug, and inspect.
2. Using the logger to send information to a log file.
3. Use the debugger gem to set breakpoints in the code and step through the code.

Question 6

How do you use the debugger gem to insert a breakpoint in the code?

Answer 6

Use the debugger call on the line you want to break at. Make sure you’ve included debugger in the gem file and are running the rails server with the debugger option.

Question 7

What are the two key priciples that Ruby is designed around?

Answer 7

1. DRY: Don’t repeat yourself
2. Convention over configuration

Question 8

How do you set the root page for your website?

Answer 8

Open config/routes.rb and add the line root ‘controller#action’. In the case of the welcome controller it would be root ‘welcome#index’

Question 9

What is rake?

Answer 9

Ruby Make, a make system built for and using Ruby.

Question 10

How do you add a link to a page in Ruby on Rails?

Answer 10

<%= link_to ‘Link Name’, path %>

Question 11

How could you display the value of a variable in the console?

Answer 11

With the puts command. E.g

puts var

Question 12

What is the simplest way to concatenate 2 strings?

Answer 12

catstring = string1 + string2

Question 13

How can you run a Ruby script from the command line?

Answer 13

1. change to the files directory and type ruby script.rb
2. Use the shebang method and place #! /usr/local/bin/ruby -w at the top of the file, and make the file executable

Question 14

What is the Ruby documentation system called?

Answer 14

RDoc

Question 15

How can you access the Ruby documentation from the command line?

Answer 15

ri class

or for specific methods use

ri class::method

Question 16

How do you define and access an array?

Answer 16

a = [1, 2, 3] or a = %w(1 2 3)

a[2] returns 3

Question 17

How can you insert a variable or call into a string?

Answer 17

**x = ‘This is a string #{x.inspect}’ **

Question 18

Describe a hash and how do you define one?

Answer 18

A hash is a type of array that contains pairs of keys and values, where the keys are unique.

h = {‘GT’ => ‘Ford’,

‘DBS’ => ‘Aston Martin’}

or using symbols

h = {one: ‘first’,

two: ‘second’}

Question 19

Write an if statment

Answer 19

if x > y

…

elseif

…

else

…

end

Question 20

Write a while loop

Answer 20

while x < y

x += 1

end

Question 21

Describe how you can pass parameters to a ruby program run from the command line

Answer 21

ruby program.rb var1 var2

in the program code the input variables can be access through the ARGV array