DRY up consecutive gsub's - How to


#1

Hi,

I have a csv file suitable for an Excel display. The file has column-
names on certain row.

In order to process subsequent rows I want to refer to their columns
symbolically using the column-names. That requires the column-names to
be cleaned up in order to create valid Ruby symbols.

The following worked fine:
if col_name
col_name.gsub!(/[\s]/, “”)
col_name.gsub!(/[&]/, “And”)
col_name.gsub!(/[#]/, “Number”)
end

Each of the following one-liners failed:
col_name.gsub!(/[\s]/, “”). gsub!(/[&]/, “And”).gsub!(/[#]/,
“Number”) if col_name
col_name.gsub(/[\s]/, “”). gsub(/[&]/, “And”).gsub(/[#]/, “Number”)
if col_name

Can either of the one-liners be made to work?

The code is show in a larger (easier to read) context at
http://www.pastie.org/442456

Thanks in Advance,
Richard

.


#2

RichardOnRails wrote:

Each of the following one-liners failed:
col_name.gsub!(/[\s]/, “”). gsub!(/[&]/, “And”).gsub!(/[#]/,
“Number”) if col_name

col_name = col_name.to_s.gsub(/[\s]/, “”). gsub(/[&]/,
“And”).gsub(/[#]/,
“Number”)

If you don’t mind col_name shifting from a nil to a blank.

Also, the [] brackets add no value - both [\s] and \s are a one-width
match.


#3

On Fri, Apr 10, 2009 at 3:30 AM, RichardOnRails
removed_email_address@domain.invalid wrote:

   if col_name

Can either of the one-liners be made to work?

The code is show in a larger (easier to read) context at http://www.pastie.org/442456

Thanks in Advance,
Richard

Here is a oneliner
col.gsub!(/[\s&#]/){ |x| x == “#” ? “Number” : x == “&” ? “And” : “” }
just to show that your code is much better.
Why do you dislike it, it is readable and simple.
If you are worried about changes, you might potentially factor that out

[ /\s/, “”, “&”, “And”, "#’, “Number”].each_slice( 2 ) do | reg, rep |
col.gsub! reg, rep
end

HTH
Robert


#4

On Apr 9, 9:25 pm, RichardOnRails
removed_email_address@domain.invalid wrote:

    if col_name

Can either of the one-liners be made to work?

The code is show in a larger (easier to read) context athttp://www.pastie.org/442456

Thanks in Advance,
Richard

.

Hi Philip and Robert,

Thank you both for great responses.

First off, I still wanted to know what was the flaw in my one-liner;
I found two:

  1. I needed carefully placed parenthesis
  2. The parenthesized version failed because I just discovered) gsub!
    returns nil when no change is made. Bad idea for my purpose; no doubt
    Matz saw a good reason for it.

Bob, your version worked fine and fulfills my goal
Ditto for your version, Robert.
For both, I appended “if if col_name” to handle unnamed columns.

With two great choices, my aesthetics lead me to Robert’s version
because:

  1. I like the x.gsub! … better than x = x.gsub …
  2. The single gsub! with the choices laid out in order packs expanding
    it for additional cases with the least typing.

Again, thank you both very much for your help.

Best wishes,
Richard

Most of all, I like one-liners much better than 5-liners for
readability.