How to do foo.chomp!.rstrip!.downcase! ?

[Geometric Patterns]

Rather than:

foo.chomp!
foo.rstrip!
foo.downcase!

...it seems like I should be able to do:

foo.chomp!.rstrip!.downcase!

...but I get: undefined method `downcase!' for nil:NilClass
(NoMethodError)

This is probably a basic ruby thing that I'm not grokking...

Many thanks in advance,

- d

 

[David A. Black]

Hi --

Rather than:

foo.chomp!
foo.rstrip!
foo.downcase!

...it seems like I should be able to do:

foo.chomp!.rstrip!.downcase!

...but I get: undefined method `downcase!' for nil:NilClass
(NoMethodError)

This is probably a basic ruby thing that I'm not grokking...

A lot of destructive ! methods return nil if the object isn't changed --
for example:

"abc".gsub!(/z/, "y")
=> nil

So it's generally best not to chain them.


David

--
David A. Black, Senior Developer, Cyrus Innovation Inc.

The Ruby training with Black/Brown/McAnally
Compleat Philadelphia, PA, October 1-2, 2010
Rubyist http://www.compleatrubyist.com

 

[Alex Stahl]

What you're likely running into is that .rstrip! returns nil if no
change was made.

Check this for more details:
http://ruby-doc.org/core/classes/String.html#M000829

-Alex

 

[Geometric Patterns]

What you're likely running into is that .rstrip! returns nil if no
change was made.

Check this for more details:
http://ruby-doc.org/core/classes/String.html#M000829

-Alex

Thank you David and Alex!

 

[Brian Candler]

Rather than:

foo.chomp!
foo.rstrip!
foo.downcase!

You could do:

foo.instance_eval { chomp!; rstrip!; downcase! }

 

[Lars Olsson]

You could do:

foo.instance_eval { chomp!; rstrip!; downcase! }

....or just don't use the "bang" versions of the methods:

foo = foo.chomp.rstrip.downcase

/lasso

 

[ara.t.howard]

...it seems like I should be able to do:

foo.chomp!.rstrip!.downcase!

you can.

%w( chomp! rstrip! downcase! ).each{|m| foo.send(m)}

-a

 

[Jason Roelofs]

you can.

%w( chomp! rstrip! downcase! ).each{|m| foo.send(m)}

-a

So... what's wrong with:

foo = foo.chomp.rstrip.downcase

Jason

 

[Josh Cheek]

[Note: parts of this message were removed to make it a legal post.]

So... what's wrong with:

foo = foo.chomp.rstrip.downcase

Jason

What is the rationale behind having them return nil if unchanged?

 

[Jesús Gabriel y Galán]

So... what's wrong with:

foo = foo.chomp.rstrip.downcase

Each call creates a copy of the string, and are all discarded along
with the original except the last one.

Jesus.

 

[Jason Roelofs]

=20
Each call creates a copy of the string, and are all discarded along
with the original except the last one.
=20
Jesus.
=20

I don't see any problem there, that's expected. Ruby has a GC, and those =
will get cleaned up appropriately.

The ! versions don't work chained, this version does. You shouldn't be =
worrying about the cost of creating 3 strings.

Jason=

 

[Jesús Gabriel y Galán]

I don't see any problem there, that's expected. Ruby has a GC, and those =

will get cleaned up appropriately.

The ! versions don't work chained, this version does. You shouldn't be wo=

rrying about the cost of creating 3 strings.

I know, regarding that, I don't see any problem either with

foo.chomp!
foo.rstrip!
foo.downcase!

Robert commented on this already (although his email was lost in some
problem with SpamAssassin, but he resent):

... which usually is less efficient. I guess OP had a reason to
use bang versions.

and I clarified. If it's three strings, no problem. If this is in a
loop you might want to reduce garbage. Just pointing out a fact about
the non-bang methods.

Jesus.

 

[Lars Olsson]

I know, regarding that, I don't see any problem either with

foo.chomp!
foo.rstrip!
foo.downcase!

Robert commented on this already (although his email was lost in some
problem with SpamAssassin, but he resent):



and I clarified. If it's three strings, no problem. If this is in a
loop you might want to reduce garbage. Just pointing out a fact about
the non-bang methods.

Jesus.

Yeah, looking at the source code for ruby 1.9 reveals that
String.chomp is essentially implemented as String.sup.chomp!, so
you're absolutely right about the non bang versions creating some
extra garbage. The same is true about (rstrip and downcase as well.)
How this affects the overall performance is really hard to say without
benchmarking though. But as Robert claimed

foo.chomp!
foo.rstrip!
foo.downcase!

is probable the most efficient way.

/lasso

 

[Lars Olsson]

Yeah, looking at the source code for ruby 1.9 reveals that
String.chomp is essentially implemented as String.sup.chomp!, so
you're absolutely right about the non bang versions creating some
extra garbage. The same is true about (rstripanddowncaseas well.)
How this affects the overall performance is really hard to say without
benchmarking though. But as Robert claimed

foo.chomp!
foo.rstrip!
foo.downcase!

is probable the most efficient way.

/lasso

Argh...it was supposed to read "implemented as String.dup.chomp!"

/lasso