From: Nick Green <cruzmail.ngreen@...>
Date: 2009-09-07T16:12:25+09:00
Subject: Re: Type checking function parameters

Lots of helpful opinions/philosophies about ruby here.

As for the respond_to? is more useful than is_a? comment, I typecheck 
almost everything with respond to (ok thats not really a "type"check... 
i... check things with respond_to?)

However, heres one issue I have, its not complicated, but its simpler to 
say in code than words:

def foo someint
    someint+7
end

if foo "hello"
   puts "hi"
else
   puts "oh noez!"
end

Putting this in irb only gives me an error.  There are times I would 
like to say, if this function works, do this, otherwise, do this.  And 
its not neccesarily unacceptable for the function to fail, but I wan't 
to know if it failed so I can do something about that.  I realize that 
many (most?) functions you just figure its bad news if it fails, but I 
have enough functions that I just redo/try something else/figure out 
whats wrong if the function fails that I need a way to say this.  In 
less fun/happy languages this looks like


ret = putButterOn(my_pancake);
if (ret != BUTTER_APPLIED)
{
   buttering_queue.enqueue(my_waffle);
   return ERROR_PANCAKE_NOT_BUTTERED;
}

And here, if  I don't really have my heart set on a buttered pancake, 
but I need to know if this putButterOn function was not build to handle 
pancakes (perhaps pancake.respond_to? "spreadButter" == false).  I 
realize this code is not really a likely way to handle things, but it 
gets the idea across.  If I don't manually check values and return 
nil/false/an error code if things go wrong, how can I keep going if a 
function call fails? This works for checking errors in irb, but an 
actual script appears to give up when it errors...

ret = putButterOn my_pancake
if ret == nil
   butter_queue.push my_waffle
end
-- 
Posted via http://www.ruby-forum.com/.