Ruby - 打印变量名，然后打印它的值

Question

编写函数(或 DSLish 的东西)的最佳方法是什么，可以让我用 Ruby 编写此代码。我将如何构建函数 write_pair？

username = "tyndall"
write_pair username
# where write_pair username outputs 
username: tyndall

可以吗？寻找最简单的方法来做到这一点。

Answer 1

当然可以!

我的解决方案通过 Object#object_id 身份测试 var:http://codepad.org/V7TXRxmL
它在绑定(bind)传递样式中被削弱了......
虽然它只适用于本地变量，但可以很容易地使其成为“通用”的，添加使用其他范围变量列表方法，如 instance_variables 等。

# the function must be defined in such a place 
# ... so as to "catch" the binding of the vars ... cheesy
# otherwise we're kinda stuck with the extra param on the caller
@_binding = binding
def write_pair(p, b = @_binding)
  eval("
    local_variables.each do |v| 
      if eval(v.to_s + \".object_id\") == " + p.object_id.to_s + "
        puts v.to_s + ': ' + \"" + p.to_s + "\"
      end
    end
  " , b)
end

# if the binding is an issue just do here:
# write_pair = lambda { |p| write_pair(p, binding) }

# just some test vars to make sure it works
username1 = "tyndall"
username  = "tyndall"
username3 = "tyndall"

# the result:
write_pair(username)
# username: tyndall