Remove object from an array of objects

Question

my problem should be rather simple, but i didn't got it.

For example i have the following data from the database:

@user = User.all

then i have an other array of user

other_user = getting_them_from_somewhere_else

Now i iterate over the two arrays and check if some users are still in the database by checking for the emails:

@other_user.each do |o|
    @user.each do |u|
        if o["email"] == u["user_mail"]
            @user.delete(u)
            break
        end
    end

    ... do something with o ...
end

The method @user.delete(u) deletes the user from the database, but i just want to remove the object u from the array @user.

@user is not an array.. it's a collection to be sure, but an activerecord collection. You can iterate across it, and do a pile of things that may feel like an array. Don't think of it as an array. It will break your heart. — baash05
– baash05, Commented Jul 30, 2013 at 3:13

megas · Accepted Answer · 2012-01-21 18:25:55Z

0

You can do vise versa

result_users = []
@other_user.each do |o|
    @user.each do |u|
        if o["email"] != u["user_mail"]
            result_users << u
        end
    end

    ... do something with o ...
end
here you should use result_users array which has the users you need

edited Jan 21, 2012 at 18:25

answered Jan 21, 2012 at 18:14

megas

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Comments

Leandro Andrade · Accepted Answer · 2013-03-28 16:19:14Z

0

You can use:

@other_user.each do |o|
   @user.delete_if{|u| u["email"] == o["email"]}
end

It's more simple, and didn't remove of database, only remove in array. =)

answered Mar 28, 2013 at 16:19

Leandro Andrade

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Comments

baash05 · Accepted Answer · 2013-07-30 03:09:46Z

0

How about going the cheaper way... Less work.. create an array of the email addresses that you know about, and don't want anymore.

other_emails = @other_user.map{|o| sanitize(o["email"]) }
@users = User.where("email not in (  #{other_emails.join(',')}  )")

There are so many pluses to this approach.

there is only one loop (the map), nothing embedded.
there is only one array resize (the map). We aren't calling delete which is a heavy operation on an array.
We only get records across the network that we care about. Pulling down 1 million records when you only care about a handful is silly. Strive to only read from the DB what you need.

Sometimes letting the database do things is just smarter.

answered Jul 30, 2013 at 3:09

baash05

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Comments

Bamboo · Accepted Answer · 2017-12-24 15:36:40Z

0

I think you don't need to use @user.email, just:

  @users.delete_if {|user| @other_user.include? user}

answered Dec 24, 2017 at 15:36

Bamboo

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