Ruby array of arrays find by inner array value

Question

I have array of arrays, which looks like this:

a = [['1','1500','SomeName','SomeSurname'],
['2','1500','SomeName2','SomeSurname2'],
['3','1500','SomeName3','SomeSurname3'],
['4','1501','SomeName','SomeSurname'],
...]

I can get sub-array of this array with all rows containing '1500' value by .each function and simple if, but if a.length is large, it's taking too much time! How can I get all rows from a with certain a[1] value, without iterating over a?

Andrey Deineko · Accepted Answer · 2015-12-10 18:59:02Z

10

Enumerable#find_all is what you are looking for:

a.find_all { |el| el[1] == '1500' } # a.select will do the same

edited Dec 10, 2015 at 18:59

answered May 12, 2015 at 11:09

Andrey Deineko

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ABrowne · Accepted Answer · 2015-05-12 11:13:47Z

7

You have a few options, you could use a find:

a.find { |l| l[1] == '5' }

This would find the array that matches the first 5

You need to use find_all to find all:

a.find_all { |l| l[1] == '5' }

edited May 12, 2015 at 11:13

answered May 12, 2015 at 10:57

ABrowne

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2 Comments

Krzysztof Witczak Over a year ago

But will it find all matches, or only the first one?

ABrowne Over a year ago

Andrey has nailed it, I missed that you wanted all

Lars Haugseth · Accepted Answer · 2015-05-12 11:11:58Z

1

Use select to get all matching elements:

a.select { |e| e[1] == '1500' }

answered May 12, 2015 at 11:11

Lars Haugseth

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