Validating array insertion in Rails

Question

I have Table1 with attribute attribute1, which is an array of integer. My controller allows for one insertion at a time. So, in the controller:

def add_attribute1_item
  table1 = Table1.find(params[:id])
  table1.attribute1 << add_params[:attribute1_item]
  table1.save!
  render json: table1
rescue
  render_errors_for(table1)
end

I want to validate this attribute1_item value, ignoring the old values that have been stored in attribute1 array, e.g. if table1.attribute1 contains 99 and I call the controller add_attribute1_item to add 100, I only want to check whether 100 is valid or not, ignoring 99.

class Task < ApplicationRecord
     .
     .
     .
  validate :attribute1_item_is_valid, if: -> { attribute1.present? }
     .
     .
     .
  def attribute1_item_is_valid
    # validate the item by accessing attribute1
  end

I am unsure with this approach because when I access attribute1 in attribute1_item_is_valid, it is the whole array instead of the new item. Is this approach good enough by calling attribute1.last() or is there a more correct method? thank you

Schwern · Accepted Answer · 2020-03-13 04:55:31Z

1

Instead of trying to validate this in the model, validate the form entry.

Create a model for the form and use normal validations.

class SomeForm
  include ActiveModel::Model

  attr_accessor :id, :attribute1_item

  validate :id, presence: true, numericality: { only_integer: true }
  validate :attribute1_item, presence: true
end

def add_attribute1_item
  form = SomeForm.new(params)
  if form.invalid?
    # render form.errors
    return
  end

  table1 = Table1.find(form.id)
  table1.attribute1 << form.attribute1_item
  table1.save!
  render json: table1
rescue
  render_errors_for(table1)
end

answered Mar 13, 2020 at 4:55

Schwern

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1 Comment

max Over a year ago

If you're using Rails 5.1+ use attribute :id, :integer and attrribute :attribute1_item instead of attr_accessor. The attributes api will create attributes that actually behave much like ActiveRecord attributes so that you can call .attributes on the model or serialize it.

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