From: dblack@...
Date: 2007-06-05T22:16:33+09:00
Subject: Re: Writing method "change!" for String

Hi --

On Tue, 5 Jun 2007, Harry Kakueki wrote:

> On 6/5/07, Mike <michaelst@gmail.com> wrote:
>> Hi,
>>
>>    I'm trying to write simple method to change internal value of
>> String class:
>> 
>> class String
>>     def change!
>>         self="0" if self.downcase=="myvalue1"
>>         self="1" if self.downcase=="myvalue2"
>>         self
>>     end
>> end
>> 
>> test="myvalue1"
>> test.change!
>> p test
>> 
>> It should just change value of string to what I want. But I get error:
>> "Can't change the value of self".
>> How do I proceed?
>> 
>> Thanks.
>> 
>> 
>> 
> Do not try to change self.
>
> Try this.
>
> class String
>  def change!
>      val="0" if self.downcase=="myvalue1"
>      val="1" if self.downcase=="myvalue2"
>      val
>  end
> end
>
> test="myvalue1"
> p test.change!
> p test

I think even the original idea probably wasn't a good !-candidate
(since bang methods generally have non-bang equivalents, whereas
methods with names that imply change or other "danger" [like replace]
don't), and definitely if you're not modifying the string or doing
anything else dangerous, the ! is not a good idea, since it's out of
keeping with the convention.


David

-- 
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