From: Florian Gross <florgro@...>
Date: 2006-07-29T18:34:57+09:00
Subject: Re: What method should a class provide for printf's %c format string ?

Gerald schrieb:

> It seems that the printf conversion to %c tries to call a specific
> method of my class to convert the object to the appropriate format. I am
> a bit confused about the message "can't convert to integer", since the
> to_i method is defined, and sucessfully called that the printf "%d"
> line.
> 
> So, two questions arise
> 
> - what method am I supposed to provied for printf so it can handle the
>   '%s' format string
> 
> - How can I figure this out myself. It seems that printf is trying to
>   call something, but I have no way of telling exactly  what  it is
>   trying to do. Is there some kind of tracing/debugging that can be
>   switched on to see what's printf is trying to do ?

I guessed that it would try to implicitly convert the object to an 
Integer. Ruby usually uses to_int() for that. to_i() is used for 
explicit conversions.

I verified that guess by doing this:

irb(main):002:0> "%c" % Class.new { def to_int() ?A end }.new
=> "A"

Hope this helps.

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