ruby multiple regexp gsub with array.inject

Question

I have to work with a long text and make some substitution with regexp inside it. Now I wrote the following code:

text = File.read(file)
replacements = [
                [/```([\w]+)/, "\n\1>"],
                [/```\n/, "\n\n"],
                [/pattern not found/, 'sub'],
                [/pattern that should be found/, 'no sub'],
               ]
replacements.inject(text) do |text, (k,v)|
    if text =~ k
        text.gsub!(k,v)
    end
end
File.write(name', text)

If every regexp is found in my document everything works fine, but if a replacements pattern is not found, all subsequent replacements are not carried out.

I put the if text =~ k but it does not work the same.

Any idea?

Aleksei Matiushkin · Accepted Answer · 2016-01-25 14:32:34Z

3

The reason is that String#gsub! returns nil if there were no substitutions made, and the result if there were. Another glitch is that you call matching twice, the check for text =~ k is redundant.

I would go with not inplace version of gsub:

result = replacements.inject(text) do |text, (k, v)|
  text.gsub(k, v)
end

the above should do the trick.

Whether you still want to use inplace substitution, you might just return text itself on unsuccessful gsub!:

result = replacements.inject(text) do |text, (k, v)|
  text.gsub!(k, v) || text
end

edited Jan 25, 2016 at 14:32

answered Jan 25, 2016 at 14:26

Aleksei Matiushkin

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Comments

martinciu · Accepted Answer · 2016-01-25 14:17:17Z

2

Each inject iteration should return memo (in your case text) to the next iteration. Try this code:

replacements.inject(text) do |text, (k,v)|
  if text =~ k
    text.gsub!(k,v)
  end
  text
end

answered Jan 25, 2016 at 14:17

martinciu

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Comments

Wand Maker · Accepted Answer · 2016-01-25 14:26:36Z

2

The block of inject must return memo value. So, you may have to change your code to do this:

replacements.inject(text) do |text, (k,v)|
    text.gsub(k,v)
end

When if test =~ k failed in your case, the block's output was nil - hence, the issue.

Alternatively, you can use with_object

replacements.each.with_object(text) do |(k,v), text|
    text.gsub!(k,v)
end

edited Jan 25, 2016 at 14:26

answered Jan 25, 2016 at 14:16

Wand Maker

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4 Comments

Aleksei Matiushkin Over a year ago

with_object has an opposite parameters order: |(k, v), text|.

Wand Maker Over a year ago

@mudasobwa Thanks, will fix it

sawa Over a year ago

You don't need the conditioning. That is some meaningless thing that the OP put.

Wand Maker Over a year ago

@sawa Arigatou gozaimasu !! Did some updates based on your feedback.

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