How to convert a string into class name?

Rails
1

I transfer a class name information (‘model’, a string) using a URL
params :id.
and I get the name using params[:id] in an controller action.
Now, how can I convert ‘model’ (string) into Model (class name) to
perform a Model.find(X)?

2

Nanyang Z. wrote:

I transfer a class name information (‘model’, a string) using a URL
params :id.
and I get the name using params[:id] in an controller action.
Now, how can I convert ‘model’ (string) into Model (class name) to
perform a Model.find(X)?

Try this:

params[:id].camelize.constantize

This will turn the string “my_super_cool_model” into the constant
(ie. the class) MySuperCoolModel.

3

Snowman wrote:

Try this:

params[:id].camelize.constantize

This will turn the string “my_super_cool_model” into the constant
(ie. the class) MySuperCoolModel.

it works! thanks.
btw, what’s the difference between .camelize and .classify?

4

btw, what’s the difference between .camelize and .classify?

You use classify when you’re starting with the plural version (eg. the
table name). So “my_super_cool_models”.classify => “MySuperCoolModel”

5

instance_variable_get("@#{object}").send(attribute)

6

I see. Thanks.

Now I know how to convert a string into a relative class name, like I
can make ‘user’ to User.

But what if I know ‘object’ (string) and ‘attribute’(string) when I want
to get a @object.attribute?
I’ll use this in helper method.

7

Sorry to revive such an old post, but I saw this and had to mention
something…

Snow Man wrote:

btw, what’s the difference between .camelize and .classify?

You use classify when you’re starting with the plural version (eg. the
table name). So “my_super_cool_models”.classify => “MySuperCoolModel”

While that’s true, classify is sometimes incorrect. Example:

‘email_address’.classify
=> “EmailAddres”

What I would suggest if you have the plural form, or if you’re not sure
what form you have, is to call singularize first, then camelize.
Example:

‘email_addresses’.singularize.camelize
=> “EmailAddress”

8

Snow Man wrote:

instance_variable_get("@#{object}").send(attribute)

Thanks!