More Neat Things Slides - Code Like This

More Neat Things About Ruby

This section is a continuation of "ruby intro", covering more advanced topics. It is still intended as a brief, lightweight overview of the Ruby language; following sections will cover all these topics in much more detail.

Reopening classes

class Fixnum
  def divisible_by? n
    self % n == 0
  end
end

4.divisible_by? 2 #=> true
4.divisible_by? 3 #=> false

Duck Typing

If it looks like a duck...
and it quacks like a duck...
then it is a duck!
In other words
- we don't care what an object is;
- we care what it does

Modules and Mixins

Any class (or object) can include a Module
- also known as mixing in
- so Modules are also called mixins
Modules provide behavior but no state
- more precisely, they affect the extending object's state
Provides most of the power of multiple inheritance, but less confusing

Array Assignment

@width, @height = width, height
@width, @height = [width, height]

def dimensions
  [10, 20]
end
@width, @height = dimensions

Metaprogramming

macros (class methods)
- attr_accessor
- has_many

Classes are objects

class methods are really just methods on the class object
code evaluated in the scope of a class definition acts on the class object

Domain-Specific Languages (DSLs)

Rails
Rake
Cucumber
Rspec
etc.

No Function Overloading

Some OO languages allow several methods with the same name but different parameters...
...but not Ruby!
If you redefine a method, the new one replaces the old one
There are tricks to save the old method if you need to call it
- alias, alias_method, alias_method_chain

Operators are Methods

Equivalent:

1 + 2
1.+(2)
1.send "+", 2

send the object 1 the message + with the parameter 2

Operator Overriding

operators like +, *, <<, etc. are defined as methods
so they can be overridden like any method
String has some great ones

"abc" * 3           #=> "abcabcabc"
"abc" << "def"      #=> "abcdef"
"%d live crew" % 2  #=> "2 live crew"

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