ruby学习--block

 #当前块
 class Block
     def a_method
         return yield if block_given?
         'no block'
     end
 end
 obj=Block.new
 puts "#{obj.a_method}"
 puts "#{obj.a_method {"here's a block!"}}"

 #闭包
 class Greeter
     def initialize(name)
         @name=name
     end
     def name
         @name
     end
     def name=(new_name)
         @name=new_name
     end
 end
 g=Greeter.new("Barney")
 puts g.name 　　　　
 g.name="Betty"
 puts g.name　　　　　　 

 #切换作用域
 v1=1
 class MyClass
     v2=2
     local_variables
     #puts "#{local_variables}"　　     #[:v2]　　
     def my_method
         v3=3
         local_variables
         #puts "#{local_variables}"    #[:v3]
     end
     local_variables
     #puts "#{local_variables}"        #[:v2]

 end
 obj=MyClass.new
 obj.my_method                        #[:v3]
 puts "#{local_variables}"            #[:v1, :obj]