CODEWITHSUNDEEP
ruby-on-railsruby
Mike
Mike

Reputation: 59

Compare incoming object with record in the database in ruby on rails

I have been trying to compare two objects in rails, the first is from a new record and the other is a record in the database but I have not achieved it, what I have been doing is the following:

def update
  new_biological_target = params[:biological_target]
  old_biological_target = BiologicalTarget.find(params[:biological_target][:id])

  if new_biological_target == old_biological_target
    message="Equals"
  else
    message="different"
  end
end

What I want to compare is that if the user made any changes to the registry

Upvotes: 0

Views: 1613

Answers (4)

ray
ray

Reputation: 5552

You can use ActiveModel::Dirty - changed?

biological_target = BiologicalTarget.find(params[:biological_target][:id])

message = biological_target.assign_attributes(params[:biological_target]).changed? ? "Different" : "Equals"

Upvotes: 1

Sean
Sean

Reputation: 287

As others have mentioned here, you are comparing two different types. I assume you are comparing a Hash and a BiologicalTarget.

One solution is to loop through new_biological_target, and compare the values of new_biological_target to the values in the old_biological_target record.

# can initially set message to equal
message = 'equal'

new_biological_target.each do |key, value|
  # make sure the record even has the attribute, then if it does, check to see if the values are the same 
  if old_biological_target.has_attribute?(key) && old_biological_target.attributes[key] == value
    # move to next iteration of loop because the attribute was the same as value
    next
  # the params you are passing either have additional keys that aren't contained in the record, so handle however you want, in this case I am saying the object is different, or the value was different for the key
  else
    message = 'different'
    break
  end
end

Upvotes: 1

jvillian
jvillian

Reputation: 20263

Possibly, assign_attributes. So, you could do something like:

  biological_target = BiologicalTarget.find(params[:biological_target][:id])
  biological_target.assign_attributes biological_target_params
  biological_target.changed?
    message = "Changed"
  else 
    message = "Unchanged"
  end

You'll want to make sure to process those parameters so you don't get a mass assignment error.

Upvotes: 0

Kris
Kris

Reputation: 19948

You are comparing to different types, params[:biological_target] is, most likely, an instance of Hash and BiologicalTarget.find is an instance of BiologicalTarget therefore == will always be false.

You could try converting your model to a Hash of attributes, as such:

new_biological_target = params[:biological_target]
old_biological_target = BiologicalTarget.find(params[:biological_target][:id]).attributes
new_biological_target == old_biological_target # => true/false

But this is unlikely to work because the params being submitted from the form will not have created_at, updated_at or id attributes, for starters.

You would be better off trying to create a new model using the params and use model validations and/or database constraints to enforce uniqueness.

Upvotes: 0

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