ActiveRecord serialize attribute not returned as a 'hash' but rather a string

Question

I have a table/class :

class User < ActiveRecord::Base
    serialize :photos
end

When I query, via something like this:

Post.joins(:user).select('users.username, users.photo AS user_photo')

This returns the photo, but not as a 'hash' but rather as the raw string stored in the database:

{
    "post_type" = 0;
    "user_id" = 1;
    "user_photo" = "---\n:photo: http://res.cloudinary.com/jhess2991/image/upload/eb29c343249624.png\n:thumb: http://res.cloudinary.com/jhess2991/image/upload/c_scale,h_180,w_180/eb29c3423429624.png\n";
    username = HDILOfficial;
}

Of course, this only happens when I query from a ActiveRecord class other than User. If I query from User (User.select(blah blah blah)) then it returns as a normal hash.

So my question is, how can I make it treat 'photo' as a hash when querying from another class?

i found a kind of a similar question there. this may helps stackoverflow.com/questions/11801484/… — devanand
– devanand, Commented Dec 19, 2013 at 9:43
some other question and answer may helps you stackoverflow.com/questions/14568983/… — devanand
– devanand, Commented Dec 19, 2013 at 15:21

Simone Carletti · Accepted Answer · 2013-12-19 13:17:32Z

0

At the time being, you can't. There is no way for ActiveRecord to know that the user_photo references the value of the photos attribute you defined in the User model.

answered Dec 19, 2013 at 13:17

Simone Carletti

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2 Comments

0xSina Over a year ago

Ok I understand it's not possible. But not sure about the 'no way it can know' part. Are you sure there's no way for AR to know that it's doing a joins on a table that has a serialize attribute? :)

Simone Carletti Over a year ago

At first glance, I assume it will not be possible without some hacks. I can't see any easy way to accomplish it.

devanand · Accepted Answer · 2013-12-19 15:25:48Z

-1

Did you see the information an api.rubyonrails.org

http://api.rubyonrails.org/classes/ActiveRecord/Base.html#label-Saving+arrays%2C+hashes%2C+and+other+non-mappable+objects+in+text+columns

Saving arrays, hashes, and other non-mappable objects in text columns

Active Record can serialize any object in text columns using YAML. To do so, you must specify this with a call to the class method serialize. This makes it possible to store arrays, hashes, and other non-mappable objects without doing any additional work.

class User < ActiveRecord::Base
  serialize :preferences
end

user = User.create(preferences: { "background" => "black", "display" => large })
User.find(user.id).preferences # => { "background" => "black", "display" => large }

You can also specify a class option as the second parameter that'll raise an exception if a serialized object is retrieved as a descendant of a class not in the hierarchy.

class User < ActiveRecord::Base
  serialize :preferences, Hash
end

user = User.create(preferences: %w( one two three ))
User.find(user.id).preferences    # raises SerializationTypeMismatch

When you specify a class option, the default value for that attribute will be a new instance of that class.

class User < ActiveRecord::Base
  serialize :preferences, OpenStruct
end

user = User.new
user.preferences.theme_color = "red"

This may helps

answered Dec 19, 2013 at 15:25

devanand

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1 Comment

devanand Over a year ago

@0xSina sorry, where is your question. btw i have a kind of holiday :) it takes some time. i am away till 6. jan

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