From: Daniel Schierbeck <daniel.schierbeck@...>
Date: 2006-07-29T00:30:06+09:00
Subject: Re: Weird problem with case expressions

ara.t.howard@noaa.gov wrote:
> On Fri, 28 Jul 2006, Daniel Schierbeck wrote:
> 
>> Thank you for the response. Yes, it seems there is no way to get 
>> around using parentheses. It's actually just an aesthetic problem; the 
>> method in question has a question mark suffix, and I like to call such 
>> methods without parentheses. Specifically, it was an attempt at an 
>> aesthetically pleasing version of the code in "Symbols are your friend":
>>
>>  case "foo"
>>    when of_type? :int then "integer"
>>    when of_type? :str then "string"
>>  end
>>
>> Unfortunately, I'll have to write it like this:
>>
>>  case "foo"
>>    when of_type?(:int) then "integer"
>>    when of_type?(:str) then "string"
>>  end
>>
>> It doesn't really matter that much though -- I'm not even sure I like 
>> that solution.
>>
>>
>> Cheers, and thanks for replying,
>> Daniel
> 
> you could do
> 
>   class Symbol
>     def like?
>       {
>         :int => Integer,
>         :str => String,
>         :ary => Array,
>       }[self] or raise 'no type!'
>     end
>   end
> 
> then
> 
>   case 'foo'
>     when :int.like? then 'integer'
>     when :str.like? then 'string'
>   end
> 
> 
> althogh i personally would use
> 
>   [Integer, String, Array].detect{|c| c === 'foo'}
> 
> since i can easily become a one liner, even with many classes.  if you need
> the string then
> 
>   [Integer, String, Array].detect{|c| c === 'foo' and c.name.downcase}

That would work, but I don't think classes and types are always the 
same. An ordered hash is still a hash, even if it doesn't descend from 
Hash. This way, all objects that respond to #to_hash is in some way a 
hash, and I can trust (to some degree) that the object returned when 
calling that method implements the interface of Hash.


Cheers,
Daniel