How do I write a custom validation method with parameters for my ActiveRecord model?

Question

In my model I have:

validate :my_custom_validation

def my_custom_validation

errors.add_to_base("error message") if condition.exists?

end

I would like to add some parameters to mycustomer vaildation like so:

validate :my_custom_validation, :parameter1 => x, :parameter2 => y

How do I write the mycustomvalidation function to account for parameters?

Answer 1

You can just do something like this:

def validate
  errors.add('That particular field', 'can not be the value you presented') if !self.field_to_check.blank? && self.field_to_check == 'I AM COOL'
end

No need to call reference it, as I believe the validate method is processed (if it exists) after any validates_uniqueness_of -like validations.

Added: More information in the Rails API docs here.

Answer 2

Validators usualy have an array parameter indicating, first, the fields to validate and lastly (if it exists) a hash with the options. In your example:

:my_custom_validation, :parameter1 => x, :parameter2 => y

:my_custom_validation would be a field name, while :parameter1 => x, :parameter2 => y would be a hash:

{:parameter1 => x, :parameter2 => y}

Therefore, you'd do something like:

def my_custom_validation(*attr)
    options = attr.pop if attr.last.is_a? Hash
    # do something with options
    errors.add_to_base("error message") if condition.exists?

end