It is probably a really simple thing but can't find a solution.
I have an ActiveRecord object and want to get an attribute like this:
attribute_name = "name"
user = User.find(1)
user.get_attribute_by_name(attribute_name) => "John"
Thanks!
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3 Answers
All of these should work:
user[attribute_name]
user.read_attribute(attribute_name)
user.send(attribute_name)
Personally I wouldn't use send in this case. When available, prefer public_send to send
6 Comments
lime
I concur that it is better to avoid
send. However if you are accessing an association rather than a plain attribute, it seems like send is your best bet.
jmarceli
Can you tell me why I should avoid
send? I'm afraid I have to use it.Frederick Cheung
@user2041318 with send you need to be extra sure that you've been passed an actual attribute name (rather than, for example, 'destroy')
shajin
If there's a wrapper plugin over the attribute (like, carrierwave), first two solutions will get u string instead of Carrierwave object. If u want attribute including wrapper class, use this
user.read_attribute_for_serialization(attribute_name) (it works, though I dont know what that fuction is for)
hiphapis
user[attribute_name] are different user.send(attribute_name). user[attr_name] => get from db field, user.send(attr_name) => get from model |
You can use either [] or read_attribute() but they are not equivalent.
The safer method of access is using the [] method method because it will raise an ActiveModel::MissingAttributeError error if the attribute does not exist. The read_attribute method returns nil if the attribute does not exist.
4 Comments
rkallensee
The read_attribute method is still present in ActiveRecord 5 and I can't find any hints about it being deprecated.
Brent Matzelle
Read this APIdock page which states the following: "This method is deprecated or moved on the latest stable version. The last existing version (v2.3.8) is shown here."
rkallensee
It was just moved to the module
ActiveRecord::AttributeMethods::Read and is still present.Brent Matzelle
I removed the notes about the function being deprecated and added some new notes on the differences between the
[] and read_attribute functions.In Rails 5, just attribute_name = "name" works
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