Database query in rails, save model as variable in controller

Question

(This is probably an easy question, but I didn't find the right words to google my problem)

In my controller I have a query like this:

information = Event.where(name: 'xyz')

Which works fine. In this case, only the model "event" gets queried and not other models like "Blog" or "Post". Instead of writing every query, I just want to call a method, which could look like this:

def find_information (model, word)
  information = model.where(name: 'word')
end

So, if I write find_information (Event, xyz), it should do:

information = Event.where(name: 'xyz')

or if I write find_information (Blog, xyz), it should do:

information = Blog.where(name: 'xyz')

I tried this:

model = Event

"#{model}".where(name: 'xyz')

But this throws an "undefined method `where' for "Event":String" error. How do I save the model in a variable? Thanks in advance

Nicolas Duval · Accepted Answer · 2016-06-19 21:25:51Z

2

You are making a query to the name attribute with the string 'word'

  information = model.where(name: 'word')

You should query the argument with word.

def find_information (model, word)
  information = model.where(name: word)
end

This works for me.
Hope this help.

answered Jun 19, 2016 at 21:25

Nicolas Duval

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Comments

Kkulikovskis · Accepted Answer · 2016-06-20 07:01:05Z

1

If you are going to make user pass the model name, when making these kinds of queries, I suggest whitelisting them:

def find_information(klass_string, query)
  whitelisted_classes = %w(Event Blog Post)
  if whitelisted_classes.include?(klass_string)
    klass = klass_string.constantize
    result = klass.where(query)
  end
end

I know it is not fully what you asked for, so to answer your original question, if you pass a class as a variable then you can use it right away

klass = Event
klass.where(query)

edited Jun 20, 2016 at 7:01

answered Jun 19, 2016 at 21:51

Kkulikovskis

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