Ruby remove empty, nil arrays strings from array of strings

Question

I have this array of arrays:

["[]", "[\"https://somewebsite1.com\"]", "[\"https://somewebsite2.com\"]", "[]", "[]", "[]", "---\n- https://somewebsite3.com\n", "--- []\n", "---\n- https://somewebsite4.com\n", "--- []\n", "--- []\n", "---\n- https://somewebsite.com\n", "---\n- https://somewebsite5.com\n", nil, nil, nil, nil, nil]

How can I:
1- remove all the empty, nil element
2- have an array of string:

["https://somewebsite1.com", "https://somewebsite2.com", "https://somewebsite3.com", "https://somewebsite4.com", "https://somewebsite.com", "https://somewebsite5.com"]

array.select &:present? remove nil
then array.delete_if {|i| i == '[]'} remove []
so I am left with :

["[\"https://somewebsite1.com\"]", "[\"https://somewebsite2.com\"]",  "---\n- https://somewebsite3.com\n", "--- []\n", "---\n- https://somewebsite4.com\n", "--- []\n", "--- []\n", "---\n- https://somewebsite.com\n", "---\n- https://somewebsite5.com\n"]

No, that's not array of arrays. That's array of strings, where strings contain what appears to be yaml code — Sergio Tulentsev
– Sergio Tulentsev, Commented Oct 31, 2017 at 15:28
A weird mix of YAML and JSON? Or is [] valid YAML, without the leading ---? — user229044
– user229044 ♦, Commented Oct 31, 2017 at 15:37

Stanislav Mekhonoshin · Accepted Answer · 2017-10-31 16:12:43Z

3

First of all, it is a simple array of strings.

You can remove nil elements using array.compact or array.reject(&:nil?)

And to remove empty yaml entries you can use deserialization

array.compact .reject { |i| YAML.parse(i).children.first.children.empty? } .map { |i| i.gsub('["', '').gsub('"]', '').gsub("---\n- ", '').strip }

So the output would be you stated.

Update:

Another approach, without string manipulation

res = a.compact
deserialized = res.map { |i| YAML.parse(i) }
res = deserialized.reject { |i| i.children.first.children.empty? }
res.map { |i| i.children.first.children.first.value }

edited Oct 31, 2017 at 16:12

answered Oct 31, 2017 at 15:53

Stanislav Mekhonoshin

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3 Comments

Sergio Tulentsev Over a year ago

Much gsub, so string manipulation, wow. :) Why not use output of YAML.parse instead? Or, better, YAML.load?

Stanislav Mekhonoshin Over a year ago

It's fast and dirty solution. Yeah, working with deserialized YAML would be much better.

Sergio Tulentsev Over a year ago

Just use YAML.load, it'll simplify code substantially. my_array.compact.map(&YAML.method(:load)).reject(&:empty?).flatten

Mark Tabler · Accepted Answer · 2017-10-31 16:24:06Z

1

To just remove nil elements, you can use the compact method on an array. To remove both nil and empty strings, you can use the select method:

my_array.select! { |element| element&.size.to_i > 0 }

To process the remaining strings, you'll need to iterate over each string and figure out whether it needs YAML parsing or not. The method you'll use to collect the results of that iteration is map:

my_array.map! { |element| clever_string_parsing_on(element) }

edited Oct 31, 2017 at 16:24

answered Oct 31, 2017 at 16:07

Mark Tabler

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2 Comments

Sergio Tulentsev Over a year ago

Have you tried your first snippet? It's not working.

Mark Tabler Over a year ago

My bad - I had tried it, but with too simple a test case; the bug didn't show up. I've edited in a fix. Good catch, and many thanks!

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