# test.rb
class Greeting
 def initialize(text)
  @text = text
 end

 def welcome
  @text
 end
end
my_obj = Greeting.new("hello")
puts my_obj.class
puts my_obj.class.instance_methods(false) #false means not inherited
puts my_obj.instance_variables

result =>
Greeting
welcome
@text

mongo API for ruby => Mongo::MongoClient

# testmongo.rb
require 'mongo'
require 'pp'

include Mongo

# the members of replcation-set
# test mongodb server version 2.6.0
host = "192.168.11.51"
# The port of members
# If the port is 27017 by default then otherport don't need to assignment
otherport = ""
port = otherport.length != 0 ? otherport : MongoClient::DEFAULT_PORT

opts = {:pool_size => 5, :pool_timeout => 10}
# Create a new connection
client = MongoClient.new(host, port, opts)

# puts client.class
puts client.class.constants
puts client.instance_variables
puts client.class.instance_methods(false)

Constant, Instance Attribute, Instance Method

class MyClass
 def my_method(args)
  args * 10
 end
end
obj = MyClass.new

puts obj.my_method(5)
puts "**"
puts obj.send(:my_method, 6)

50
**
60

obj.send(:my_method, 6)

puts 1.send(:+, 4) => 5
String#to_sym(),String#intern() => string to symbol
String#to_s(),String#id2name() => symbol to string
"caoqing".to_sym() => :caoqing
:caoqing.to_s() => "caoqing"

puts obj.class.instance_methods(true).delete_if{ |method_name| method_name !~ /^my/}
result => 
my_method

class MyClass
 define_method :my_method do |args|
  args * 3
 end
end
obj = MyClass.new
puts obj.my_method(10)

# test.rb
str = "My name is caoqing."
def str.title?
 self.upcase == self
end

puts str.title?
puts str.methods.grep(/^title?/)
puts str.singleton_methods

false
title?
title?

obj.my_method
Cla.class_method

def obj.method
 # method body
end

class << obj
 code
end

# test.rb
class Foo
 @@var = "lion"
 def self.method01
  puts "cat"
  @name = "cat"
  @@var = "cat"
  puts @name
 end

 def self.method02
  puts "tiger"
  @name = "tiger"
  @@var = "tiger"
  puts @name
 end

 def self.method03
  puts "dog"
  @name = "dog"
  @@var = "dog"
  puts @name
 end

 def putsname
  puts @name
  puts @@var
 end
end

obj = Foo.new
# obj.method01   => (NoMethodError)

obj.putsname   => lion

Foo.method01
Foo.method02
Foo.method03
obj.putsname

lion
cat
cat
tiger
tiger
dog
dog

dog