Array to String Back to Array Conversion Problem

Question

I'm saving a bunch of ID's to the session like this.

session[:id_group] = 1,2,3,4,5

Because I need to save them to a data base with a form.

In that form I have hidden-field :

<%= form.text_field :group, :value => session[:id_group].inspect%>

I use the inspect so that the value saved to the database gets to be [1,2,3,4,5] and not 12345

The problem is, when I get that value from the DB I get [1,2,3,4,5] as a String. If I do:

groups = game.group
=> [1,2,3,4,5]
group.class 
=>string

I can convert it to an array like this:

groups = game.group.split(',')

but then if I do


groups.each |group| do
  puts |group|.to_s
end

I get

And I need the clean ID's so I can do something like


but then if I do
groups.each |id| do
  User.find_by_id(id)
end

How can I fix this mess? Thanks in advance.

tadman · Accepted Answer · 2010-02-12 22:01:36Z

2

You shouldn't be encoding your values using inspect. That will get re-encoded into a literal string, which is probably not your intention.

The correct way to put things in your form is to do the opposite of how you want to decode them:

<%= form.text_field :group, :value => session[:id_group].join(',') %>

Where join and split are matched up properly, it will work. The counterpart to inspect is eval and you really do not want to do that as someone can run arbitrary code that way.

As a note, you can also load a bunch of users with a single query using something like:

@ids = params[:group].split(/,/)

@users = User.find_all_by_id(@ids)

This is much more efficient than loading them in one at a time.

answered Feb 12, 2010 at 22:01

tadman

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Community · Accepted Answer · 2017-05-23 12:30:15Z

0

See: Convert a stringified array back to array

groups.class
#=> String
groups = JSON.parse(groups)
#=> [1,2,3,4,5]
groups.class
#=> Array

edited May 23, 2017 at 12:30

CommunityBot

11 silver badge

answered Nov 20, 2015 at 16:27

bradleygsmith

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