Rails 3 check if attribute changed

Question

Need to check if a block of attributes has changed before update in Rails 3   street1  street2  city  state  zipcode  I know I could use something like  if  user street1    params  user   street1    then do something     end   But that piece of code will be REALLY long   Is there a cleaner way

User · Answer

Above answers are better but yet for knowledge we have another approch as well, Lets 'catagory' column value changed for an object (@design),

@design.changes.has_key?('catagory')

The .changes will return a hash with key as column's name and values as a array with two values [old_value, new_value] for each columns. For example catagory for above is changed from 'ABC' to 'XYZ' of @design,

@design.changes   # => {} 
@design.catagory = 'XYZ'
@design.changes # => { 'catagory' => ['ABC', 'XYZ'] }

For references change in ROR

User · Answer

ActiveModel  Dirty didn t work for me because the  model update attributes   hid the changes  So this is how I detected changes it in an update method in a controller   def update    model   Model find params  id     detect changes    if  model update attributes params  model       do stuff if attr changed    end end  private  def detect changes    changed         changed  lt  lt   attr if  model attr    params  model   attr  end  def attr changed     changed include  attr end   If you re trying to detect a lot of attribute changes it could get messy though   Probably shouldn t do this in a controller  but meh

User · Answer

For rails 5 1  callbacks  As of Ruby on Rails 5 1  the attribute changed  and attribute was ActiveRecord methods will be deprecated  Use saved change to attribute  instead of attribute changed    user saved change to street1      gt  true false   More examples here

User · Answer

This is how I solved the problem of checking for changes in multiple attributes   attrs     street1    street2    city    state    zipcode    if   user changed  amp  attrs  any    then do something     end   The changed method returns an array of the attributes changed for that object   Both  user changed and attrs are arrays so I can get the intersection  see ary  amp  other ary method   The result of the intersection is an array  By calling any  on the array  I get true if there is at least one intersection   Also very useful  the changed attributes method returns a hash of the attributes with their original values and the changes returns a hash of the attributes with their original and new values  in an array    You can check APIDock for which versions supported these methods   http   apidock com rails ActiveModel Dirty

User · Answer

Check out ActiveModel  Dirty  available on all models by default   The documentation is really good  but it lets you do things such as    user street1 changed      gt  true false

[ruby-on-rails] Rails 3 check if attribute changed

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