ActiveRecord: make query using model from a string

Question

I have a string containing a set of ActiveRecord models and I would like to do the same query for every model passed as string.

model_type = 'Comment'
id = 1
record = model_type.find(id)

model_type = 'Post'
id = 1
record = model_type.find(id)

How can I do that?

tadman · Accepted Answer · 2010-11-12 21:21:08Z

4

You need to use the constantize method.

model_type.constantize.find(id)

Do be careful when accepting arbitrary user data and evaluating it like this. You may generate exceptions for unknown classes.

answered Nov 12, 2010 at 21:21

tadman

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Comments

Dan Harper · Accepted Answer · 2010-11-13 00:03:37Z

1

constantize nice, I hadn't seen that one before. Here's how I've done it in the past:

@list = Kernel.const_get(@type).find_by_id_and_account_id(params[:id], current_account.id)

I'm not sure which is better, constantize looks cleaner :)

answered Nov 13, 2010 at 0:03

Dan Harper

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