ruby api设计

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#先看一段source code

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f = File.open("myfile.txt", 'w')
f.write("Lorem ipsum dolor sit amet")
f.write("Lorem ipsum dolor sit amet")
f.close
                ||
                \/
# using block
File.open("myfile.txt", 'w') do |f|
  f.write("Lorem ipsum dolor sit amet")
  f.write("Lorem ipsum dolor sit amet")
end

#如上，是使用block后的效果，再来一段

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# without code block
def send_message(msg)
  socket = TCPSocket.new(@ip, @port) # Pre-
  socket.puts(msg)
  response = socket.gets
  ensure
    socket.close # Post-
  end
end
            ||
            \/
# with code block
def send_message(msg)
  connection do |socket|
    socket.puts("foobar")
    socket.gets
  end
end
def connection
  socket = TCPSocket.new(@ip, @port) # Pre-
    yield(socket)
    ensure
      socket.close # Post-
    end
end

#Module 的使用

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module Mixin
   def foo
       puts "foo"
   end
end
class A
    include Mixin
end
A.new.foo # foo

.使用extend(Mod)

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module Mixin
    def foo
        puts "foo"
    end
class A
  extend Mixin
end
end
A.extend(Mixin)
A.foo # class method
the same as
class << A
  include Mixin
end

.obj.extend(Mod)
如下

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module Mixin
     def foo
         puts "foo"
     end
end
a = "test"
a.extend(Mixin)
a.foo # foo
the same as
class << a
  include Mixin
end
b = "demo"
b.foo # NoMethodError

.Mixin with class methods

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module Mixin
  def foo
    puts "foo"
  end
  module ClassMethods
    def bar
      puts "bar"
    end
  end 
end
class MyClass
  include Mixin
  extend Mixin::ClassMethods
end

等同于如下代码：

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module Mixin
  # self.included is a hook method
  def self.included(base)
    base.extend(ClassMethods)
  end
  def foo
    puts "foo"
  end
  module ClassMethods
    def bar
      puts "bar"
    end
  end 
end
class MyClass
  include Mixin
end

等同于：

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module Mixin
  def self.included(base)
    base.extend(ClassMethods)
    base.send(:include, InstanceMethods)
  end
  module InstanceMethods
    def foo
      puts "foo"
    end
  end
  module ClassMethods
    def bar
      puts "bar"
    end
  end 
end
class MyClass
  include Mixin
end