Java转Ruby【快速入门】

irb
irb(main):001:0> puts "Hello World!"
Hello World!
=> nil

irb(main):002:0> properties = ['name','age','sex']
=> ["name", "age", "sex"]
irb(main):003:0> properties
=> ["name", "age", "sex"]
irb(main):005:0> properties.each {|property| puts "This is #{property}."}
This is name.
This is age.
This is sex.
=> ["name", "age", "sex"]

# bad - four spaces
def some_method
    do_something
end

# good
def some_method
  do_something
end

# bad
puts 'foobar'; # superfluous semicolon

puts 'foo'; puts 'bar' # two expression on the same line

# good
puts 'foobar'

puts 'foo'
puts 'bar'

puts 'foo', 'bar' # this applies to puts in particular

# bad
def too_much; something; something_else; end

# okish - notice that the first ; is required
def no_braces_method; body end

# okish - notice that the second ; is optional
def no_braces_method; body; end

# okish - valid syntax, but no ; make it kind of hard to read
def some_method() body end

# good
def some_method
  body
end

# good
def no_op; end

# bad - pretty convoluted
kind = case year
when 1850..1889 then 'Blues'
when 1890..1909 then 'Ragtime'
when 1910..1929 then 'New Orleans Jazz'
when 1930..1939 then 'Swing'
when 1940..1950 then 'Bebop'
else 'Jazz'
end

result = if some_cond
  calc_something
else
  calc_something_else
end

# good - it's apparent what's going on
kind = case year
       when 1850..1889 then 'Blues'
       when 1890..1909 then 'Ragtime'
       when 1910..1929 then 'New Orleans Jazz'
       when 1930..1939 then 'Swing'
       when 1940..1950 then 'Bebop'
       else 'Jazz'
       end

result = if some_cond
           calc_something
         else
           calc_something_else
         end

# good (and a bit more width efficient)
kind =
  case year
  when 1850..1889 then 'Blues'
  when 1890..1909 then 'Ragtime'
  when 1910..1929 then 'New Orleans Jazz'
  when 1930..1939 then 'Swing'
  when 1940..1950 then 'Bebop'
  else 'Jazz'
  end

result =
  if some_cond
    calc_something
  else
    calc_something_else
  end

def some_method
  data = initialize(options)

  data.manipulate!

  data.result
end

def some_methods
  result
end

# bad
== begin
comment line
another comment line
== end

# good
# comment line
# another comment line

# bad
def some_method()
  # body omitted
end

# good
def some_method
  # body omitted
end

# bad
def some_method_with_arguments arg1, arg2
  # body omitted
end

# good
def some_method_with_arguments(arg1, arg2)
  # body omitted
end

arr = [1, 2, 3]

# bad
for elem in arr do
  puts elem
end

# note that elem is accessible outside of the for loop
elem #=> 3

# good
arr.each { |elem| puts elem }

# elem is not accessible outside each's block
elem #=> NameError: undefined local variable or method `elem'

# bad
if condition
  result = x
else
  result = y
end

# good
result =
  if condition
    x
  else
    y
  end

# boolean expression
if some_condition && some_other_condition
  do_something
end

# control flow
document.save? or document.save!

# bad
unless success?
  puts 'failure'
else
  puts 'success'
end

# good
if success?
  puts 'success'
else
  puts 'failure'
end

# bad
if (x > 10)
  # body omitted
end

# good
if x > 10
  # body omitted
end

# bad
class SomeClass
  def self.some_method
    # body omitted
  end

  def self.some_other_method
  end
end

# good
module SomeClass
  module_function

  def some_method
    # body omitted
  end

  def some_other_method
  end
end

module Utilities
  extend self

  def parse_something(string)
    # do stuff here
  end

  def other_utility_method(number, string)
    # do some more stuff
  end
end

# good
module Utilities
  module_function

  def parse_something(string)
    # do stuff here
  end

  def other_utility_method(number, string)
    # do some more stuff
  end
end

class Person
  attr_reader :first_name, :last_name

  def initialize(first_name, last_name)
    @first_name = first_name
    @last_name = last_name
  end

  def to_s
    "#@first_name #@last_name"
  end
end

# good
class Person
  attr_reader :first_name, :last_name

  def initialize(first_name, last_name)
    @first_name = first_name
    @last_name = last_name
  end
end

# better
class Person < Struct.new(:first_name, :last_name)
end

# good
class Person
  attr_accessor :first_name, :last_name

  def initialize(first_name, last_name)
    @first_name = first_name
    @last_name = last_name
  end
end

# better
Person = Struct.new(:first_name, :last_name) do
end

# bad
class Animal
  # abstract method
  def speak
  end
end

# extend superclass
class Duck < Animal
  def speak
    puts 'Quack! Quack'
  end
end

# extend superclass
class Dog < Animal
  def speak
    puts 'Bau! Bau!'
  end
end

# good
class Duck
  def speak
    puts 'Quack! Quack'
  end
end

class Dog
  def speak
    puts 'Bau! Bau!'
  end
end

# bad
email_with_name = user.name + ' <' + user.email + '>'

# good
email_with_name = "#{user.name} <#{user.email}>"

# good
email_with_name = format('%s <%s>', user.name, user.email)

# good and also fast
html = ''
html << '<h1>Page title</h1>'

paragraphs.each do |paragraph|
  html << "<p>#{paragraph}</p>"
end

:abcd

irb(main):011:0> "string".object_id
=> 26922000
irb(main):012:0> "string".object_id
=> 29115220
irb(main):013:0> :symbol.object_id
=> 788188
irb(main):014:0> :symbol.object_id
=> 788188

{"key1" => "value1", "key2" => "Chemistry", "key3" => "Maths"}

data = {"key1" => "Physics", "key2" => "Chemistry", "key3" => "Maths"}   
puts data["key1"]   
puts data["key2"]   
puts data["key3"]

Physics
Chemistry
Maths

$global_var = "GLOBAL"   
class One   
  def display   
     puts "Global variable in One is #$global_var"   
  end   
end   
class Two   
  def display   
     puts "Global variable in Two is #$global_var"   
  end   
end   

oneobj = One.new   
oneobj.display   
twoobj = Two.new   
twoobj.display

Total number of states written: 4
Total number of states written: 4
Total number of states written: 4
Total number of states written: 4

class States   
   def initialize(name)   
      @states_name=name   
   end   
   def display()   
      puts "States name #@states_name"   
    end   
end   

# Create Objects   
first=States.new("Hainan")   
second=States.new("GuangDong")   
third=States.new("Beijing")   
fourth=States.new("ShangDong")   

# Call Methods   
first.display()   
second.display()   
third.display()   
fourth.display()

States name GuangDong
States name Beijing
States name ShangDong

class States   
   @@no_of_states=0   
   def initialize(name)   
      @states_name=name   
      @@no_of_states += 1   
   end   
   def display()   
     puts "State name #@state_name"   
    end   
    def total_no_of_states()   
       puts "Total number of states written: #@@no_of_states"   
    end   
end   

# Create Objects   
first=States.new("Assam")   
second=States.new("Meghalaya")   
third=States.new("Maharashtra")   
fourth=States.new("Pondicherry")   

# Call Methods   
first.total_no_of_states()   
second.total_no_of_states()   
third.total_no_of_states()   
fourth.total_no_of_states()

Total number of states written: 4
Total number of states written: 4
Total number of states written: 4
Total number of states written: 4

Object newObject = new Object(); // Java 中新建对象

objectName = className.new

class ClassName  
    codes...  
end

class Person
  attr_reader :first_name, :last_name

  def initialize(first_name, last_name)
    @first_name = first_name
    @last_name = last_name
  end

  def to_s
    "#@first_name #@last_name"
  end
end

def methodName  
    code...  
end

def method_defining(a1 = "Ruby", a2 = "Python")
   puts "The programming language is #{a1}"
   puts "The programming language is #{a2}"
end
method_defining "C", "C++"
method_defining

The programming language is C
The programming language is C++
The programming language is Ruby
The programming language is Python

def my_method
   i = 100
   j = 10
   k = 1
end

def method
   i = 100
   j = 200
   k = 300
return i, j, k
end
var = method
puts var

100
200
300

def sample (*test)
   puts "The number of parameters is #{test.length}"
   for i in 0...test.length
      puts "The parameters are #{test[i]}"
   end
end
sample "Maxsu", "6", "F"
sample "Mac", "38", "M", "MCA"

The number of parameters is 3
The parameters are Maxsu
The parameters are 6
The parameters are F
The number of parameters is 4
The parameters are Mac
The parameters are 38
The parameters are M
The parameters are MCA

class Accounts
   def reading_charge
   end
   def Accounts.return_date
   end
end

Accounts.return_date

module A
  def a1
  end
  def a2
  end
end
module B
  def b1
  end
  def b2
  end
end

class Sample
  include A
  include B
  def s1
  end
end

samp=Sample.new
samp.a1
samp.a2
samp.b1
samp.b2
samp.s1

block_name{
   statement1
   statement2
   ..........
}

def test
   puts "在 test 方法内"
   yield
   puts "你又回到了 test 方法内"
   yield
end
test {puts "你在块内"}

在 test 方法内
你在块内
你又回到了 test 方法内
你在块内

def test
  yield
end
test{ puts "Hello world"}

def test(&block)
   block.call
end
test { puts "Hello World!"}

Hello World!