Ruby on Rails - Adding arrays to column

Question

If I have a Playlist model, how can I push arrays into a column?

#<Playlist id: 1, title: "This is a playlist", songs_ids: 1>

And want to push arrays to the songs_ids column what do I have to do?

This is how the songs_ids column look like

add_column :playlists, :songs_ids, :integer, array: true, default: []

I've tried updating the attributes and adding annother id of a song to it, but I have no luck with it either:

Playlist.find(1).update_attribute(songs_ids: [1, 2])

Possible duplicate of Rails: Adding migration to add an array (default empty) — Adam Zapaśnik
– Adam Zapaśnik, Commented Mar 29, 2017 at 17:09
Are you serialising the array in your model class? serialize :song_ids, Array in Playlist.rb apidock.com/rails/ActiveRecord/Base/serialize/class — KyleHodgetts
– KyleHodgetts, Commented Mar 29, 2017 at 17:15
@muistooshort I am using mysql database for development and postgres for production — Bad Hombre
– Bad Hombre, Commented Mar 29, 2017 at 17:40
AFAIK MySQL doesn't support array columns so your songs_ids is just an int. There are so many differences between MySQL and PostgreSQL that ActiveRecord will not help you with that developing on MySQL and deploying on PostgreSQL is madness. Develop and test with PostgreSQL if that's what you're deploying on. Rails/ActiveRecord doesn't offer any useful support for database portability beyond that absolute basics. — mu is too short
– mu is too short, Commented Mar 29, 2017 at 17:43

Sebastián Palma · Accepted Answer · 2017-03-29 18:17:11Z

1

If you're using Postgresql you can simply use the update_all method to update array columns in your model.

Playlist.where(id: 1).update_all(songs_ids: [1,2])

Note it won't work with Playlist.find(1)....

Using Mysql you can consider to serialize to do this you must use a string type column.

 def change
    add_column :playlists, :songs_ids, :string
  end

Then specify the attribute which to serialize in your model.

class Playlist < ActiveRecord::Base 
    serialize :songs_ids, Array 
end

Then you can test pushing any value to it.

playlist = Playlist.first
playlist.songs_ids << 1
=> [1]
playlist.save
playlist.songs_ids << 2
=> [2]
playlist.save
playlist.songs_ids
=> [1, 2]

edited Mar 29, 2017 at 18:17

answered Mar 29, 2017 at 17:41

Sebastián Palma

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2 Comments

Sebastián Palma Over a year ago

Tested in Postgresql this works, on Mysql it doesn't, this one keeps the songs_ids attribute as nil after the operation.

Bad Hombre Over a year ago

It doesn't work even if I serialize because as you've mentioned I think it's to do with the database, and I'm guessing that's the only workaround for this?

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