Ruby 基础笔记

=begin
注释内容
=end

puts "hello world"
print "hello world"

"hello world"
'hello world'

# 方式1，显示创建方法
Range.new(1, 10) # 元素为 1～10
# 方式2
1..10 # 元素为 1～10
# 方式3
1...10 # 元素为 1～9

do...end

{...}

# 多行代码块
10.times do |i|
  puts i
end

# 单行代码块
10.times {|i| puts i}

begin
  可能会发生异常的代码
rescue => 引用异常对象的变量（不指明对象将异常赋值给 $!）
  发生异常后的处理
end

begin
  File.read('/etc/passwd1')
rescue => e
  puts e
end

begin
  File.read('/etc/passwd1')
rescue
  puts $!
end

begin
  File.read('/etc/passwd1')
rescue
  puts [email protected]
end

# 创建一个模块
module LX
  # 模块常量
  Version = "1.0"

  def say(msg)
    puts msg
  end

  # 获得模块自身信息，保存在 self 变量中
  def self_object
    self
  end

  # 不这么定义的函数或者类，只能在上下文中引用，
  # 不能被外部引用以“模块名.方法名”引用
  module_function :say
end

module LX
  Version = "1.0"

  def say(msg)
    puts msg
  end
end

s1 = "hi"
s1.extend(LX)
s1.say(s1) # => hi

a = Array.new

class NewString < String
  def hi
    puts "hi"
  end
end

s = NewString.new("hi")
puts s
s.hi

# coding: utf-8

class Hello
  def initialize(msg)  # 构造函数
    @msg = msg  # 成员变量
  end

  def show_msg
    puts @msg # 引用成员变量
  end

  def msg # 外部不能直接访问成员变量，需要定义“存取器”
    @msg
  end

  def msg=(new_msg)
    @msg = new_msg
  end
end

hello = Hello.new("hi")
hello.show_msg
puts hello.msg
hello.msg = 'new msg'
hello.show_msg

class << Hello
  def say(msg)
    puts msg
  end
end

Hello.say("new hello")

class Hello
  attr_reader :msg
  attr_writer :msg
  # 实现读写直接用 attr_accessor :msg

  class << self
    def say(msg)
      puts msg
    end
  end

  def initialize(msg)  # 构造函数
    @msg = msg  # 成员变量
  end

  def show_msg
    msg = 'hi'
    puts self.msg # 引用成员变量
  end
end

hello = Hello.new("hi")
hello.show_msg
Hello.say("new hello")

def Hello.say(msg)
    puts msg
end

def self.say(msg) # 因为还在 class 的上下文中，所以能这么定义
  puts msg
end

class TheI
 @@count = 0

  def count
    puts @@count
  end

  def plus
     @@count += 1
  end
end

the_i1 = TheI.new
the_i1.count
the_i2 = TheI.new
the_i2.count

the_i1.plus
the_i1.count # => 1
the_i2.count # 也是 1

class Hi
  def self_known
    puts 'self'
  end

  def you_known
    puts 'you known'
  end

  def i_want_access_self_known
    self_known
  end

  # 设置访问级别
  public :you_known # 默认就是 public
  private :self_known
end

hi = Hi.new
hi.you_known
hi.i_want_access_self_known

class Hi
  # 以下方法都为 private 级别
  private
  def self_known
    puts 'self'
  end

  # 以下方法都为 public 级别
  public
  def you_known
    puts 'you known'
  end

  def i_want_access_self_known
    self_known
  end
end

hi = Hi.new
hi.you_known
hi.i_want_access_self_known

class String
  def hi
    puts "hi"
  end
end

s = "hello"
s.hi

class C1
  def hello
    puts "hello"
  end
end

class C2 < C1
  alias old_hello hello # 别名化父类的“hello”方法

  # 重定义 hello
  def hello
    puts "hello world"
  end
end

c = C2.new
puts c.hello
puts c.old_hello

class C1
  def hello
    puts "hello"
  end

  def say(msg)
    puts msg
  end
end

class C2 < C1
  alias old_hello hello

  # 重定义 hello
  def hello
    puts "hello world"
  end

  # 不要父类中的 say 方法
  undef say
end

c = C2.new
puts c.hello
puts c.old_hello
c.say('hi')

str1 = "Ruby"
str2 = "Ruby"

class << str1
  def say(msg)
    puts msg
  end
end

str1.say("hehe")
str2.say("hehe") # => undefined method `say' for "Ruby":String

module LX
  Version = "1.0"

  def say(msg)
    puts msg
  end
end

class C
  include LX
end

c = C.new
c.say("hehe")

class Stream
end

module Reader
  def read
    puts 'read'
  end
end

module Writer
  def write
    puts 'write'
  end
end

class Read < Stream
  include Reader
end

class Write < Stream
  include Writer
end

class ReadAndWrite
  include Reader
  include Writer
end

rw = ReadAndWrite.new
rw.read # => read
rw.write # => write

# refine需要定义一个模块
module StringExt
    refine String do
        def say(msg)
            puts msg
          end
      end
end

using StringExt # 明确使用了 using 关键字，扩展类才会生效
'hi'.say('hello world')

# refine 需要定义一个模块
module StringExt
    refine String do
        def say(msg)
            puts msg
          end
      end
end

module Say
    using StringExt
    'hi'.say('hello world') # hello world
end

'hi'.say('hello world') # undefined method `say' for "hi":String (NoMethodError)