How to Delete Strings that Start with Certain Characters in Ruby

Question

I have strings of the following pattern showing up in an array:

"@SomeUselessText"

In this example, I'd like to get rid of all strings in my array that start with the character "@".

This is what I've come up with so far:

def array_purge(array)
  for array.each |item|
    item = item.gsub(/@.*/, "")
  end
end

However, this also gets rid of valid email address of the form:

"info@SomeSite.com"

...which I'd like to keep.

I'm guessing there is an elegant way of handling this. Perhaps using ".reject!"

Maybe you can use [`String#start_with?`](http://ruby-doc.org/core-2.4.1/String.html#method-i-start_with-3F) — Sagar Pandya, Apr 29 '17 at 03:21
I doubt the code posted does anything (or ever understood by ruby parser.) — Aleksei Matiushkin, Apr 29 '17 at 04:47

score 7 · Answer 1 · answered Apr 29 '17 at 03:34

The other suggested answers do not in fact purge the targeted items from the array; they merely replace the items with empty strings. More likely you want this:

def array_purge(array)
  array.reject! { |item| item.start_with?('@') }
end

>> array = ['Hello', '123', '@SomeUselessText', 'info@SomeSite.com']
>> array_purge(array)
=> ["Hello", "123", "info@SomeSite.com"]

score 1 · Answer 2 · answered Apr 07 '18 at 12:33

1

You can use Enumerable#grep_v here

array = ['Hello', '123', '@SomeUselessText', 'info@SomeSite.com']
array.grep_v(/\A@/)
 #=> ["Hello", "123", "info@SomeSite.com"]

answered Apr 07 '18 at 12:33

Sagar Pandya

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Thanks to moveson since I used his array for my example. – Sagar Pandya Apr 07 '18 at 12:34

vallentin · Accepted Answer · 2017-04-29T03:11:50.623

0

Check if there's a whitespace (\s) before or if it's the start of the string (^).

(?:\s|^)@.*

Live Demo

If you only want to match word characters, then instead of using . you could use \w. Also note that * would still match just "@", so you might want to use + instead to match at least one character.

(?:\s|^)@\w+

Live Demo

edited Apr 29 '17 at 03:11

answered Apr 29 '17 at 03:06

vallentin

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2

`^` is **not** start of the string. It’s start of the line within string. `\A` is a proper start of the string matcher. – Aleksei Matiushkin Apr 29 '17 at 04:44
@mudasobwa only if the multiline flag is set, which it is not. – vallentin Apr 29 '17 at 15:12
The requirement is "_get rid of all strings in my array that start with the character "@"_". This doesn't answer the question. – the Tin Man May 12 '17 at 22:07

score -1 · Answer 4 · answered Apr 29 '17 at 03:06

-1

Use the following regular expression [line] instead: a.gsub(/^@.*/, "")

The ^ means "from the start of the line"... so, it only matches if there's the start of the line, then the next character is an @

answered Apr 29 '17 at 03:06

RyanWilcox

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Never use `^` matcher in such a case. Use `\A` instead. `^` would match in `"abc\n@def"`. – Aleksei Matiushkin Apr 29 '17 at 04:43
This doesn't solve the problem, it results in an empty string. – the Tin Man May 12 '17 at 22:08

How to Delete Strings that Start with Certain Characters in Ruby

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