remove items in 1 ruby array from another array

Question

I have one array in rails, which for the sake of simplicity, we shall say is

@users = current_account.users

I have several other arrays, which contains subsets of that first array. These look like this

@missing_genders = @users.select{ |u| u.gender.nil?}
@missing_reference = @users.select{ |u| u.reference_number.nil?}

I have a few others like this too. What I need is to produce a list of all the users who are NOT erroneous. so basically everyone in the first array, who does not exist in any of the other arrays?

thinking through it, I have

@main_array = [1,2,3,4,5]
@error_array_1 = [1]
@error_array_2 = [1,2,3]

And I am looking to generate

@final_array = [4,5]

possible duplicate of Subtracting one Array from another in Ruby — AGS
– AGS, Commented Jan 28, 2015 at 14:04

Grych · Accepted Answer · 2015-01-28 13:36:14Z

4

The answer is really easy, you want to subtract the error_arrays from the main array, like this:

@final_array = @main_array - @error_array_1 - @error_array_2
=> [4, 5]

answered Jan 28, 2015 at 13:36

Grych

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hirolau · Accepted Answer · 2015-01-28 14:09:03Z

0

This is the way to do it if you have many arrays:

main_array = [1,2,3,4,5,6]
error_array_1 = [1]
error_array_2 = [1,2,3]
error_array_4 = [6]

p [main_array,error_array_1,error_array_2,error_array_4].reduce(:-) #=> [4, 5]

answered Jan 28, 2015 at 14:09

hirolau

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