Pragmatic Programmers - The Ruby Object Model and Metaprogramming screencastEnglish | MOV | Audio: aac 44100Hz 64 b/s | Video: qtrle 207kb/s 3000.00 fps(r) | 550Mb
Genre: eLearningEpisode 1: Objects and Classes (29 minutes)
Just what is a Ruby object, and how can Ruby move you away from class-oriented development and back to object-oriented development? Learn about:
the internals of objects,
how classes really aren’t anything special,
what self does, and the two ways it can get changed
the method call mantra: “one to the right, then up,”
singleton methods and ghost classes,
why class methods don’t exist,
how classes get their names,
how the concept of the current class interacts with def
Episode 2: Sharing Behavior (39 minutes)
One of the primary goals of good design is to put the right behavior in the right place without duplication. We’ll see three ways Ruby excels at this:
Using prototype-based programming, where you can create hierarchies of objects with controlled sharing of both state and behavior, and without a class definition in sight.
using inheritance (but you can only watch this section after you’ve watched the included Public Safety announcement on why inheritance is normally a bad idea). We’ll also look at what happens when you do class << object (and why it’s nothing whatsoever to do with inheritance).
using modules and mixins, the sweet spot of Ruby programming. How to using include and extend, and how to create modules that mix in both instance and class methods.
Episodes 1 and 2 are the foundation for the rest of the screencast.
Episode 3: Dynamic Code (31 minutes)
Metaprogramming is sometimes defined as “writing code that writes code.” Here we’ll see just how to do that in Ruby.
Blocks and the two kinds of block-objects
How bindings capture execution context
How blocks can act as closures, and why that’s vital to metaprogramming
Writing methods that define other methods using nested defs
Using define_method
Writing your own accessor methods
Episode 4: instance_eval and class_eval (29 minutes)
Two of the workhorse methods of metaprogramming are instance_eval and class_eval. They allow you to execute chunks of code dynamically. Here we’ll see how to use them.
How instance_eval and class_eval differ
When to use one versus the other
Breaking down barriers
Creating methods on the fly, but without using closures
Defining stuff in classes given a class object
Writing DSLs in a block structure
Episode 5: Nine Examples of Metaprogramming (36 minutes)
Here’s where all the theory and practice comes together! We’ll take a simple problem and find nine different ways of attacking it using metaprogramming techniques.
Adding behavior directly inside the class
Using subclassing to add behavior
Subclassing with a generator using Class.new
Using a ghost class
Ghost class with a generator using class_eval
Rewrite the method with alias_method
Rewrite using a module
Rewrite using bind
Writing a DSL in a block
Episode 6: Some Hook Methods (35 minutes)
Ruby hook methods are a way for your application to hook itself into the execution of the Ruby interpreter. Using hook methods is crucial for some kinds of metaprogramming, and they can make your code more flexible. In this episode, we’ll see how to use two powerful hook methods: inherited and const_missing.
Overriding hook methods to intercept and deal with certain Ruby interpreter events during the lifetime of your application
Decoupling code using inherited to keep track of subclasses
Implementing enumerated types with const_missing
Using const_missing to autoload classes based on the names of files
Applying const_missing in both global and localized situations
How to chain an overridden hook method to its original hook method
Using const_set to define constants
Two practical uses for hook methods
Episode 7: More Hook Methods (53 minutes)
We’ll pick up where we left off in the last episode by looking at two more Ruby hook methods: included and method_added. But we’ll also take it a step further. We’ll use these hook methods to develop a metaprogramming library that traces the execution of a Ruby program. Along the way we’ll see all the various subtle (and important!) things you need to think about when you’re trying to write a general-purpose metaprogramming library.
Using included to intercept when a module is included in a class, and use it to set up another hook method in a different context
Using method_added to track when a new method is defined on a class, and trace the method’s execution
Refactoring the tracing to support blocks
Using method objects to bypass naming issues
Adding tracing to methods that have already been added
Suppressing tracing for certain methods
Using Thread.current to define thread-local variables
Differences between Ruby 1.8 and 1.9
Practical examples (and corner cases) of metaprogramming
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