How to validate input which depends on checkbox - ruby-on-rails

Question

I recently started with rails.
I have one task here, but I don't know what is best practice and how to do it.
I have form with checkbox currency? and input currency_code.
Only value currency_code will be stored in database.
What I need:
1. If checkbox currency? is TRUE => currency_code must be filled
2. If checkbox currency? is FALSE => currency_code will be reset to nil
How to validate 1. if currency? is not in database (table column) so model does not know about this?
In case 2. Where I should check this and reset value currency_code to nil?
For case 2. I have this in my controller, but I don't like. I think that there must be a better solution.
def data_params
parameters = params.require(:data).permit(
:currency_code
)
parameters[:currency_code] = nil unless params[:data][:currency].to_bool
parameters
end

Answer 1

The attribute 'currency?' which is not part of the model is called virtual attributes. In Rails, we can use virtual attributes by setting
attr_accessor :currency?
in your corresponding_model.rb.
Now you can use this 'currency?' attribute in your form like other model attributes.
For case 2, the plcaement for this kind of data validations is to validate them in the view before even coming into the model. you must use jquery / javascript or any script of your choice. Here I provide jQuery snippet.
If you are new for using jquery in rails app, follow this https://github.com/rails/jquery-rails
In your form_page.html.erb add ids to the html elements.
<%= f.check_box :currency?, id: 'currency_checkbox' %>
and
<%= f.text_field :currency_code, id: 'currency_code' %>
The jquery snippet
curreny_checkbox = $('#curreny_checkbox')
currency_code = $('#currency_code')
$(currency_checkbox).on('change', function(){
if(this.checked)
currency_code.val('2')
else
currency_code.val('')
})
In your controller, you can simply assign the values
def create
// other codes //
#obj.currency_code = params[:currency_code]
end

Answer 2

If you want to validate input on model level you should store the currency? in the database.
Still let say for some unexplained reasons you don't want to store currency? in you database(which I won't suggest you in any case). You can define a method in model.
def set_currency_if_required is_currency_required
self.currency_code = nil unless is_currency_required
end
in controller
def create
model = Model.new(data_params)
model.set_currency_if_required(params[:data][:currency].to_bool)
model.save
end
...
def data_params
parameters = params.require(:data).permit(
:currency_code
)
end
this way you will have better readability and a clear idea about whats going on with the code.