Ruby 元编程编写代码的代码

原创于 2013-09-08 20:59:00 发布 · 862 阅读

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#Ruby #元编程 #编写代码的代码

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本文通过示例介绍了Ruby语言中使用eval动态执行代码的方法，instance_eval进行对象内部操作的应用，以及通过send方法调用对象方法的过程。此外，还展示了如何定义自定义类并在其上使用钩子函数inherited。

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1.Kernel#eval

2.0.0p247 :428 >   array = ['10','20']
 => ["10", "20"] 
2.0.0p247 :429 > element = '30'
 => "30" 
2.0.0p247 :430 > eval('array << element')
 => ["10", "20", "30"] 
2.0.0p247 :431 >

对比方法与块

.0.0p247 :422 >   array = ['a','b','c
2.0.0p247 :423'> ']
 => ["a", "b", "c\n"] 
2.0.0p247 :424 > x = 'abc'
 => "abc" 
2.0.0p247 :425 > array.instance_eval "self[1] = x"
 => "abc" 
2.0.0p247 :426 > array
 => ["a", "abc", "c\n"] 
2.0.0p247 :427 >

2.0.0p247 :450 > def explore_array(method,*arg)
2.0.0p247 :451?>   ['a','b','c'].send(method, *arg)
2.0.0p247 :452?>   end
 => nil 
2.0.0p247 :453 > explore_array(:size)
 => 3 
2.0.0p247 :454 >

2.钩子函数 inherited (更多如 module的included,method_added,method_removed,method_undefined)

2.0.0p247 :463 >   class String
2.0.0p247 :464?>    def self.inherited(subclass)
2.0.0p247 :465?>     puts "钩子函数"
2.0.0p247 :466?>     end
2.0.0p247 :467?>   end
 => nil 
2.0.0p247 :468 > class MyString < String;end
钩子函数
 => nil 
2.0.0p247 :469 >