如何设置“以编程方式”\“迭代”每个类对象属性的值？

Question

我使用Ruby on Rails的3.0.9和RSpec 2.我想通过以下方式重构了一些规范文件（为了用更少的代码相似的类对象来测试属性值）：

[ 
    :attribute_a, 
    :attribute_b, 
    :attribute_c 
].each do |attr| 
    before do 
    # HERE I would like to set the "current" 'attr' related to the 
    # class object instance 'attribute_<letter>' (read below for 
    # more information) each time the iterator is called (note: all 
    # following attributes are NOT attr_accesible - for that reason 
    # I use the 'user.attribute_<letter>' in the 'before do' 
    # statement) 
    # 
    # # Iteration 1 
    #  user.attribute_a = 'a_value' 
    # # No changes to 'user.attribute_b' 
    # # No changes to 'user.attribute_c' 
    # 
    # # Iteration 2 
    # # No changes to 'user.attribute_a' 
    #  user.attribute_b = 'a_value' 
    # # No changes to 'user.attribute_c' 
    # 
    # # Iteration 3 
    # # No changes to 'user.attribute_a' 
    # # No changes to 'user.attribute_b' 
    #  user.attribute_c = 'a_value' 

    # Maybe I should make something like the following but that, as well 
    # as the 'send' method must be used, doesn't work (the below code-line 
    # is just an example of what I would like to do). 
    # 
    # user.send(:"#{attr}") = 'a_value' 
    end 

    ... 
end 

我如何改进上面的代码，以达到我的目标（我指的是user.send(:"#{attr}") = 'a_value'部分，以“编程”方式设置 - 即为每次迭代设置不同的属性值 - 每个用户属性值为'a_value'）？

Answer 1

您应该使用.send，并追加一个=方法名调用设置，传递值作为第二个参数send：

[ 
    :attribute_a, 
    :attribute_b, 
    :attribute_c 
].each do |attr| 
    before do 
    user.send("#{attr}=", 'a_value') 
    end 

你有效地这样做：

user.send('attribute_a=', 'a_value'); 

由于几个原因，您的语法（user.send(:"#{attr}") = 'a_value'）是错误/奇怪的：

• 没有理由来:attr转换为字符串，并将其立即回符号
• 不能将值分配给的.send

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