how to test if is a property is a foreign key

rubyonrails-talk
1

You may find this project interesting.

http://drysql.rubyforge.org/features.htm

Paolo

2

From what i've read, right on the first page they are going the other way I want. Due to the nature of the project i must put the relation in the model, i'm not allowed to modify the database schema.(and the schema does not have de fk specified).

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>

Reflecting on associations might get you halfway there:

class Account < AR   has_many :users end

Account.reflect_on_association :users

=> #<ActiveRecord::Reflection::AssociationReflection:0x202491c @active_record=Account, @primary_key_name="account_id", @macro=:has_many, @name=:users, @options={}>

Account.reflections will show you all associations

Fire up ./script/console and play around.

Hope this helps.

3

thank u for the anser, does rails has equivalent for my functions?

# knowing an attribute name i want to know if it is used in a belong to relation

def self.attribute_links_to_a_class?(aatribute)     larray = reflect_on_all_associations(:belongs_to)     lreturn = false     larray.map {|n| if n.primary_key_name.eql?(aatribute);lreturn=true end}     lreturn end

Here is a one liner that is simpler.

self.reflect_on_all_associations(:belongs_to).map{ |r| r.primary_key_name }.include?(attr)

# knowing an attribute name i want the linked class to be returned

def self.if_attribute_links_to_a_class_return_class(aatribute)     larray = reflect_on_all_associations(:belongs_to)     lreturn = nil     larray.map {|n| if n.primary_key_name.eql?(aatribute);lreturn=larray.index(n) end}     if lreturn       return Object.const_get(larray[lreturn].class_name.humanize)     else       return nil     end end

This syntax might be better suited for your second method:

User.reflections[:account].class_name.constantize

Keep in mind that if the relation is of certain types like :through or :polymorphic then the class_name() method will throw an error. You'll need to check the options {} on the reflection:

reflection.options[:polymorphic] || reflection.options[:through]

It might help to play around in ./script/console with your models to check out the varying behaviour.