Opposite .nil?

[starmaerker]

I’ve looked around, but could not find a method that is the opposite of
.nil?. I know there is !my_var.nil?, but I think my_var.exists? is more
readable.

I wanted to throw this out there before I added the method in myself.

thanks,
andy

[starmaerker]

Andrew S. wrote:

I’ve looked around, but could not find a method that is the opposite of
.nil?. I know there is !my_var.nil?, but I think my_var.exists? is more
readable.

I wanted to throw this out there before I added the method in myself.

thanks,
andy

if not my_var.nil?

is the same as

if my_var

unless my_var is false.

-Justin

[starmaerker]

if not my_var.nil?

Thanks Justin. I should have been more clear with the usage.

def should_this_be_done?
am_I_sure? && my_object.var && !my_object.var.nil?
end

I just think it would read better if the last test was
my_object.var.exists?

thanks,
andy

[starmaerker]

1. No such opposite-of-nil? method exists. If you want it, add it.

Thanks for actually answering my question. Much appreciated.

2. In the particular example above (which I realize is just an

example) you could write that as:

def should_this_by_done?
am_I_sure? unless !my_object || my_object.var.nil?
end

But, of course, that just moves the negation.

Sure, I was just looking for a more readable construct. Thanks again
for
your reply.

[starmaerker]

On Dec 11, 11:56 am, Andrew S. [email protected] wrote:

I just think it would read better if the last test was my_object.var.exists?

1. No such opposite-of-nil? method exists. If you want it, add it.

class Object
def exists?
true
end
end

class NilClass
def exists?
false
end
end

up to you if you want this for FalseClass, too

2. In the particular example above (which I realize is just an
   example) you could write that as:

def should_this_by_done?
am_I_sure? unless !my_object || my_object.var.nil?
end

But, of course, that just moves the negation.

[starmaerker]

def should_this_be_done?
am_I_sure? && my_object.var && !my_object.var.nil?
end

Ooops… meant

def should_this_be_done?
am_I_sure? && my_object && !my_object.var.nil?
end

Didn’t mean to put add .var on the second test.

[starmaerker]

On Dec 11, 2007, at 3:03 PM, Andrew S. wrote:

Sure, I was just looking for a more readable construct. Thanks
again for
your reply.

I’d suggest not_nil?

class Object
def not_nil?
!self.nil?
end
end

exists? or not_nil? are both awkward if you actually have
a reference to false:

 condition = (2 > 3)      # condition is false

 if condition.exists?
    # this branch will run because condition is not nil
 else
    # do something else
 end

I think it would be clearer to be explicit about your intent
if you really want to bundle up false with true-behaving
objects:

 if condition or (condition == false)
   # do something
 end

In practice, I’ve rarely come across a situation where I wanted
to treat a false reference the same as a reference to a ‘real’
object.

Gary W.

[starmaerker]

On Dec 11, 12:56 pm, “Andrew S.” [email protected] wrote:

thanks,
andy

Andrew S.

There’s no reason to say myobject.var && !my.object.var.nil? Any
object that passes the first test is not nil.

The only reason to check !obj.nil? is if you want false to be an
accepted value.

[starmaerker]

On Dec 11, 3:03 pm, Andrew S. [email protected] wrote:

end

But, of course, that just moves the negation.

Sure, I was just looking for a more readable construct. Thanks again for
your reply.

–
Andrew S.

what about

def should_this_be_done?
am_1_sure? && my_object.var && my_object.var
end

KISS

[starmaerker]

There’s no reason to say myobject.var && !my.object.var.nil? Any
object that passes the first test is not nil.

Please see the followup email I sent.

thanks,
andy

[starmaerker]

On 11.12.2007 20:00, Andrew S. wrote:

am_I_sure? && my_object && !my_object.var.nil?
end

Didn’t mean to put add .var on the second test.

Well, you could do

am_I_sure? && my_object && my_object.var

It’s not exactly the same but if you don’t care whether my_object.var is
nil or false or if you know that it never will be false then it’s ok.

Kind regards

robert

[starmaerker]

On Dec 11, 2007 6:27 PM, Gary W. [email protected] wrote:

  !self.nil?
else

In practice, I’ve rarely come across a situation where I wanted
to treat a false reference the same as a reference to a ‘real’
object.

Gary W.

I definitely wanted a true opposite of .nil? and I do agree the term
exists?
is a little awkward, but it was the first term that people seem to use
when
thinking of !nil?. btw, this was not the result of some huge internet
poll
with thousands of responses, just 4 people, so…eh, it was good enough
for
me.

Phrogz mentioned the possibility of adding it to the FalseClass as well,
but
that’s not my intention for this method. False is a value just like an
empty string is a value where nil is the absence of value. Now I know
some
will argue that the absence of a value is a value. True and fair enough
and
a reason why the exists? method wouldn’t be added to the False class to
return a false value. false.exists? == true.

I don’t run across this scenario often. Today was just one of those
days
that I decided to look a little further into the possibilities.

Gary and Robert, thanks for the responses,
andy

[starmaerker]

On Dec 11, 2007 7:10 PM, Ken B. [email protected] wrote:

2. In the particular example above (which I realize is just an
   for your reply.

You’re not forced to program Ruby like it’s C.

–Ken

–
Ken (Chanoch) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/ http://www.iit.edu/~kbloom1/

very true Ken. I come from Java land myself and I guess old habits
die
hard.

thanks for the response,
andy

[starmaerker]

On Dec 11, 7:02 pm, Ken B. [email protected] wrote:

Here’s a more readable construct:

Hmm… maybe ‘readable’ is in the eye of the beholder

def should_this_be_done?
am_I_sure? and my_object and not my_object.var.nil?
end

Folks should be aware of the difference in precedence. In particular,
&& has a higher precedence than =, but ‘and’ has a lower precedence
than =.

You’re not forced to program Ruby like it’s C.

Agreed

[starmaerker]

On Tue, 11 Dec 2007 15:03:53 -0500, Andrew S. wrote:

def should_this_by_done?
am_I_sure? unless !my_object || my_object.var.nil?
end

But, of course, that just moves the negation.

Sure, I was just looking for a more readable construct. Thanks again
for your reply.

def should_this_be_done?
am_I_sure? && my_object && !my_object.var.nil?
end

Here’s a more readable construct:

def should_this_be_done?
am_I_sure? and my_object and not my_object.var.nil?
end

You’re not forced to program Ruby like it’s C.

–Ken

[starmaerker]

Facets has #non_nil? and #not_nil?. It also has #val? for not nil or
false or not empty if enumerable. Not to mention #false? and #true?

T.