定义用于Ruby中元编程的方法参数 [英] Define method parameters for meta programming in Ruby

问题描述

在Ruby中，我们可以使用元编程来定义实例方法，例如:

In Ruby, we can define instance methods with meta-programming like:

define_method(:hi) { 'Hello, SO world!' } # => :hi
hi                                        # => "Hello, SO world!"

通过这种方式，可以使用动态名称定义一个方法:

This way, it is possible to define a method with a dynamic name:

dynamic_name = :hi                                 # => :hi
define_method(dynamic_name) { 'Hello, SO world!' } # => :hi
hi                                                 # => "Hello, SO world!"

我们还可以将参数注入动态方法:

We can also inject arguments in to a dynamic method:

dynamic_name = :hi # => :hi
define_method(dynamic_name) do |arg1, arg2, &block|
  'Hello, SO world!'
end                # => :hi
hi(42, 42) { 42 }  # => "Hello, SO world!"

到目前为止，很好.

但是我们该怎么做才能注入动态参数? 可以用动态符号替换arg1, arg2, &block吗?

But how could we do to inject dynamic arguments? Would it be possible to replace arg1, arg2, &block by a dynamic notation?

感谢任何提示，最佳做法，甚至想法.

Thanks for any tips, best practices, or even ideas.

修改:

换句话说，我也想动态地定义实例方法的参数和块.

In other words, I would like to dynamically also define the parameters and the block of an instance method.

但是，我想使用特定数量的参数(可能为0)，一个数组作为选项，并完成该方法的块.

However, I would like to do so with a particular number of parameters (which could be 0), an array in option, and to finish the block of the method.

这样，我可以避免使用诸如以下的方法:

This way, I could avoid having methods such as:

dynamic_name = :hi      # => :hi
define_method(dynamic_name) do |*args, &block|
  'f'
end                     # => :hi
hi                      # => "f"
hi(:foo)                # => "f"
hi(:foo, :fooo)         # => "f"
hi(:foo, :fooo, :foooo) # => "f"

...这是胡说八道，因为在这里我们可以为该方法提供无限数量的未使用参数.我想避免这种情况.

...which is a nonsense, because here we can give to the method an infinite number of unused parameters. I would like to avoid this situation.

编辑2 :

原因如下:

在Ruby中，当我们需要不需要任何参数的方法时，我们可以简单地做到:

In Ruby, when we need a method which do not need any parameters, we can simply do:

def my_method
  "Hello, SO world!"
end

但是，如果相反，我会这样做:

However, if instead I do this:

def my_method(*args)
  "Hello, SO world!"
end

...结果仍然相同，但是由于参数(数组args)没有用，因此最好通过将其从方法中删除来保持简单.

...the result is still the same, but because the parameter (the array args) is useless, it would be better to keep it simple by removing it from the method.

推荐答案

尝试传递数组或字典.

更新:

if condition1
  class_eval <<-EVAL
    def #{"my_method"}(arg1)
    end
  EVAL
else  
    class_eval <<-EVAL
      def #{"my_method"}
      end
  EVAL
end

UPDATE2:

if condition1
  self.instance_eval <<-EVAL
    def #{"my_method"}(arg1)
    end
  EVAL
else  
    self.instance_eval <<-EVAL
      def #{"my_method"}
      end
  EVAL
end

UPDATE3:

# or
self.instance_eval("def method1(arg1) puts 'hellowa' + arg1.to_s; end")
self.instance_eval("def method2() puts 'hellowa2'; end")

# and then
method1(33) # => hellowa33
method2 # => hellowa2

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