- Dedication
- Author of Head First Ruby
- How to Use This Book: Intro
- 1. More with Less: Code the Way You Want
- The Ruby philosophy
- Get Ruby
- Use Ruby
- Use Ruby—interactively
- Your first Ruby expressions
- Math operations and comparisons
- Strings
- Variables
- Everything is an object!
- Calling a method on an object
- Let’s build a game
- Input, storage, and output
- Running scripts
- Comments
- “puts” and “print”
- Method arguments
- “gets”
- Parentheses are optional on method calls
- String interpolation
- What’s in that string?
- Inspecting objects with the “inspect” and “p” methods
- Escape sequences in strings
- Calling “chomp” on the string object
- What methods are available on an object?
- Generating a random number
- Converting to strings
- Ruby makes working with strings easy
- Converting strings to numbers
- Conditionals
- The opposite of “if” is “unless”
- Loops
- Let’s try running our game!
- Your Ruby Toolbox
- Up Next...
- 2. Methods and Classes: Getting Organized
- Defining methods
- Calling methods you’ve defined
- Method names
- Parameters
- Optional parameters
- Return values
- Returning from a method early
- Some messy methods
- Too many arguments
- Too many “if” statements
- Designing a class
- What’s the difference between a class and an object?
- Your first class
- Creating new instances (objects)
- Breaking up our giant methods into classes
- Creating instances of our new animal classes
- Updating our class diagram with instance methods
- Our objects don’t “know” their names or ages!
- Too many arguments (again)
- Local variables live until the method ends
- Instance variables live as long as the instance does
- Encapsulation
- Attribute accessor methods
- Using accessor methods
- Attribute writers and readers
- Attribute writers and readers in action
- Ensuring data is valid with accessors
- Errors—the “emergency stop” button
- Using “raise” in our attribute writer methods
- Our complete Dog class
- Your Ruby Toolbox
- Up Next...
- 3. Inheritance: Relying on Your Parents
- Copy, paste... Such a waste...
- Mike’s code for the virtual test-drive classes
- Inheritance to the rescue!
- Defining a superclass (requires nothing special)
- Defining a subclass (is really easy)
- Adding methods to subclasses
- Subclasses keep inherited methods alongside new ones
- Instance variables belong to the object, not the class!
- Overriding methods
- Bringing our animal classes up to date with inheritance
- Designing the animal class hierarchy
- Code for the Animal class and its subclasses
- Overriding a method in the Animal subclasses
- We need to get at the overridden method!
- The “super” keyword
- A super-powered subclass
- Difficulties displaying Dogs
- The Object class
- Why everything inherits from the Object class
- Overriding the inherited method
- Your Ruby Toolbox
- Up Next...
- 4. Initializing Instances: Off to a Great Start
- Payroll at Chargemore
- An Employee class
- Creating new Employee instances
- A division problem
- Division with Ruby’s Fixnum class
- Division with Ruby’s Float class
- Fixing the salary rounding error in Employee
- Formatting numbers for printing
- Format sequences
- Format sequence types
- Format sequence width
- Format sequence width with floating-point numbers
- Using “format” to fix our pay stubs
- When we forget to set an object’s attributes...
- “nil” stands for nothing
- “/” is a method
- The “initialize” method
- Employee safety with “initialize”
- Arguments to “initialize”
- Using optional parameters with “initialize”
- “initialize” does an end-run around our validation
- “initialize” and validation
- Call other methods on the same instance with “self”
- When “self” is optional
- Implementing hourly employees through inheritance
- Restoring “initialize” methods
- Inheritance and “initialize”
- “super” and “initialize”
- Same class, same attribute values
- An inefficient factory method
- Class methods
- Our complete source code
- Your Ruby Toolbox
- Up Next...
- 5. Arrays and Blocks: Better Than Loops
- Arrays
- Accessing arrays
- Arrays are objects, too!
- Looping over the items in an array
- The repeating loop
- Eliminating repetition...the WRONG way...
- Chunks of code?
- Blocks
- Defining a method that takes blocks
- Your first block
- Flow of control between a method and block
- Calling the same method with different blocks
- Calling a block multiple times
- Block parameters
- Using the “yield” keyword
- Block formats
- The “each” method
- The “each” method, step-by-step
- DRYing up our code with “each” and blocks
- Blocks and variable scope
- Using “each” with the “refund” method
- Using “each” with our last method
- Our complete invoicing methods
- We’ve gotten rid of the repetitive loop code!
- Utilities and appliances, blocks and methods
- Your Ruby Toolbox
- Up Next...
- 6. Block Return Values: How Should I Handle This?
- A big collection of words to search through
- Opening the file
- Safely closing the file
- Safely closing the file, with a block
- Don’t forget about variable scope!
- Finding array elements we want, with a block
- The verbose way to find array elements, using “each”
- Introducing a faster method...
- Blocks have a return value
- How the method uses a block return value
- Putting it all together
- A closer look at the block return values
- Eliminating elements we don’t want, with a block
- The return values for “reject”
- Breaking a string into an array of words
- Finding the index of an array element
- Making one array that’s based on another, the hard way
- Making one array based on another, using “map”
- Some additional logic in the “map” block body
- The finished product
- Your Ruby Toolbox
- Up Next...
- 7. Hashes: Labeling Data
- Counting votes
- An array of arrays...is not ideal
- Hashes
- Hashes are objects
- Hashes return “nil” by default
- nil (and only nil) is “falsy”
- Returning something other than “nil” by default
- Normalizing hash keys
- Hashes and “each”
- A mess of method arguments
- Using hashes as method parameters
- Hash parameters in our Candidate class
- Leave off the braces!
- Leave out the arrows!
- Making the entire hash optional
- Typos in hash arguments are dangerous
- Keyword arguments
- Using keyword arguments with our Candidate class
- Required keyword arguments
- Your Ruby Toolbox
- Up Next...
- 8. References: Crossed Signals
- Some confusing bugs
- The heap
- References
- When references go wrong
- Aliasing
- Fixing the astronomer’s program
- Quickly identifying objects with “inspect”
- Problems with a hash default object
- We’re actually modifying the hash default object!
- A more detailed look at hash default objects
- Back to the hash of planets and moons
- Our wish list for hash defaults
- Hash default blocks
- Hash default blocks: Assigning to the hash
- Hash default blocks: Block return value
- Hash default blocks: A shortcut
- The astronomer’s hash: Our final code
- Using hash default objects safely
- Hash default object rule #1: Don’t modify the default object
- Hash default object rule #2: Assign values to the hash
- The rule of thumb for hash defaults
- Your Ruby Toolbox
- Up Next...
- 9. Mixins: Mix It Up
- The media-sharing app
- The media-sharing app...using inheritance
- One of these classes is not (quite) like the others
- Option one: Make Photo a subclass of Clip
- Option two: Copy the methods you want into the Photo class
- Not an option: Multiple inheritance
- Using modules as mixins
- Mixins, behind the scenes
- Creating a mixin for comments
- Using our comments mixin
- A closer look at the revised “comments” method
- Why you shouldn’t add “initialize” to a mixin
- Mixins and method overriding
- Avoid using “initialize” methods in modules
- Using the Boolean “or” operator for assignment
- The conditional assignment operator
- Our complete code
- Your Ruby Toolbox
- Up Next...
- 10. Comparable and Enumerable: Ready-Made Mixes
- Mixins built into Ruby
- A preview of the Comparable mixin
- Choice (of) beef
- Implementing a greater-than method on the Steak class
- Constants
- We have a lot more methods to define...
- The Comparable mixin
- The spaceship operator
- Implementing the spaceship operator on Steak
- Mixing Comparable into Steak
- How the Comparable methods work
- Our next mixin
- The Enumerable module
- A class to mix Enumerable into
- Mixing Enumerable into our class
- Inside the Enumerable module
- Your Ruby Toolbox
- Up Next...
- 11. Documentation: Read the Manual
- Learning how to learn more
- Ruby’s core classes and modules
- Documentation
- HTML documentation
- Listing available classes and modules
- Looking up instance methods
- Instance methods denoted with # in the docs
- Instance method documentation
- Arguments in call signatures
- Blocks in call signatures
- Read the docs for the superclass and mixins, too!
- Read the docs for the superclass and mixins, too! (continued)
- Pool Puzzle
- Pool Puzzle Solution
- Looking up class methods
- Class method documentation
- Docs for a class that doesn’t exist?!
- The Ruby standard library
- Looking up classes and modules in the standard library
- Where Ruby docs come from: rdoc
- What rdoc can deduce about your classes
- Adding your own documentation, with comments
- The “initialize” instance method appears as the “new” class method
- Your Ruby Toolbox
- Up Next...
- 12. Exceptions: Handling the Unexpected
- Don’t use method return values for error messages
- Using “raise” to report errors
- Using “raise” by itself creates new problems
- Exceptions: When something’s gone wrong
- Rescue clauses: A chance to fix the problem
- Ruby’s search for a rescue clause
- Using a rescue clause with our SmallOven class
- We need a description of the problem from its source
- Exception messages
- Our code so far...
- Different rescue logic for different exceptions
- Exception classes
- Specifying exception class for a rescue clause
- Multiple rescue clauses in one begin/end block
- Updating our oven code with custom exception classes
- Trying again after an error with “retry”
- Updating our oven code with “retry”
- Things you want to do no matter what
- The ensure clause
- Ensuring the oven gets turned off
- Your Ruby Toolbox
- Up Next...
- 13. Unit Testing: Code Quality Assurance
- Automated tests find your bugs before someone else does
- A program we should have had automated tests for
- Types of automated tests
- MiniTest: Ruby’s standard unit-testing library
- Running a test
- Testing a class
- A closer look at the test code
- Red, green, refactor
- Tests for ListWithCommas
- Getting the test to pass
- Another bug to fix
- Test failure messages
- A better way to assert that two values are equal
- Some other assertion methods
- Removing duplicated code from your tests
- The “setup” method
- The “teardown” method
- Updating our code to use the “setup” method
- Your Ruby Toolbox
- Up Next...
- 14. Web Apps: Serving HTML
- Writing web apps in Ruby
- Our task list
- Project directory structure
- Browsers, requests, servers, and responses
- Sinatra takes requests
- Downloading and installing libraries with RubyGems
- Installing the Sinatra gem
- A simple Sinatra app
- Your computer is talking to itself
- Request type
- Resource path
- Sinatra routes
- Multiple routes in the same Sinatra app
- A route for the list of movies
- Making a movie list in HTML
- Accessing the HTML from Sinatra
- A class to hold our movie data
- Setting up a Movie object in the Sinatra app
- ERB embedding tags
- The ERB output embedding tag
- Embedding a movie title in our HTML
- Pool Puzzle
- Pool Puzzle Solution
- The regular embedding tag
- Looping over several movie titles in our HTML
- Letting users add data with HTML forms
- Getting an HTML form for adding a movie
- HTML tables
- Cleaning up our form with an HTML table
- There’s still more to do
- Your Ruby Toolbox
- Up Next...
- 15. Saving and Loading Data: Keep It Around
- Saving and retrieving form data
- Our browser can GET the form...
- ... But it needs to POST the response
- Setting the HTML form to send a POST request
- Setting up a Sinatra route for a POST request
- Converting objects to and from strings with YAML
- Saving objects to a file with YAML::Store
- Saving movies to a file with YAML::Store
- A system for finding Movies in the YAML::Store
- Numeric IDs for Movies
- Finding the next available movie ID
- A class to manage our YAML::Store
- Using our MovieStore class in the Sinatra app
- Testing the MovieStore
- Loading all movies from the MovieStore
- Loading all movies from the MovieStore (continued)
- Loading all movies in the Sinatra app
- Building HTML links to individual movies
- Building HTML links to individual movies (continued)
- Named parameters in Sinatra routes
- Using a named parameter to get a movie’s ID
- Defining routes in order of priority
- Finding a Movie in the YAML::Store
- An ERB template for an individual movie
- Finishing the Sinatra route for individual movies
- Let’s try it all out!
- Our complete app code
- Your Ruby Toolbox
- Up Next...
- A. Leftovers: The top ten topics (we didn’t cover)
- B. This isn’t goodbye
- C. O’reilly®: Ruby
- Index
- About the Author
- Copyright
About the Author
Jay McGavren was doing automation for a hotel services company when a colleague introduced him to Programming Perl (a.k.a. the Camel Book). It made him an instant Perl convert, as he liked actually writing code instead of waiting for a 10-person development team to configure a build system. It also gave him the crazy idea to write a technical book someday.
In 2007, with Perl sputtering, Jay was looking for a new interpreted language. With its strong object-orientation, excellent library support, and incredible flexibility, Ruby immediately won him over. He's since used Ruby for two game libraries, a generative art project, in support of a Java development job, and as a Ruby on Railsfreelancer. He's been using Rails in the online developer education space since 2011.
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