Dynamically get attribute value of ActiveRecord object

Question

How do I dynamically get an attribute value of an ActiveRecord object?

for example, I have a variable named attr_name.
I want to do something like this:

person = Person.find(1)
attr_name = 'address'
# address = person.<function_name>(attr_name)

which function_name can be used?

Samnang · Accepted Answer · 2012-02-28 14:07:31Z

35

Either use person.attributes[attr_name] or person.read_attribute(att_name), or even shorter then this is person[attr_name].

answered Feb 28, 2012 at 14:07

Samnang

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4 Comments

Bert Goethals Over a year ago

This is the safest and correct way. Note that this will only work for attributes, not other methods, or associations.

Nick Res Over a year ago

Unable to get attributes or methods with the object[symbol or string] syntax. Create a simple class and make some variable or method publicly accessible with the dot syntax first to see it works, then try to access it via symbol or string.. no worky.

Nick Res Over a year ago

``` class Foo def initialize @foo = 'foo name' @bar = 'bar name' end def foo @foo end end foo = Foo.new foo[:foo] ```

aristotll Over a year ago

@NickRes that is activerecord only.

Syed Aslam · Accepted Answer · 2012-02-28 11:59:14Z

5

send is the method you're looking for.

answered Feb 28, 2012 at 11:59

Syed Aslam

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2 Comments

Bert Goethals Over a year ago

depending where the function names comes from, this could be quite dangerous, so I would not do that

Joshua Pinter Over a year ago

If you're just getting the attribute value dynamically then I would definitely use something like [] or attributes[] or read_attribute. It's clearer and less dangerous. But, to do really dynamic things, you'll need send.

Abram · Accepted Answer · 2015-08-25 01:59:59Z

1

If doing this using send

address = person.send("function_name" + "attr_name")

answered Aug 25, 2015 at 1:59

Abram

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1 Comment

Joshua Pinter Over a year ago

If you're just getting the attribute value dynamically then I would definitely use something like [] or attributes[] or read_attribute. It's clearer and less dangerous. But, to do really dynamic things, you'll need send.

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