Validate with conditions

[aviscasillas]

I just want to set starting point with conditional validations.
I think it'd be cool to provide some feature to execute validations just in some defined contexts.
In this PR I'm adding the :if option as a very silly way to provide this.

[sxross]

This is really great. Also parallels the way Rails can handle validations. Here are a couple of requests:

• It would be good to make procs work :if -> (row) { row.password.match(/[0-9]/) != nil }
• It would be good to have a contextual example of when this kind of validation is useful

By the way, this is failing in Travis. Sometimes Travis needs a refresh to pass.

Thanks again!

[aviscasillas]

Oops! sorry for the failing tests, they go green locally 😓.

And agree with you! would be better to get it working with procs too, so I've written just the first step. I thought on something like this:

validate :some_column, presence: true, if: -> { some_accessor == my_desired_value }

But I'm not sure about how could I access the model attributes implicitly from inside the block. Do you know what I mean? Do you know how can I do it?

My use case by the moments works well with what is done in this PR:
I have a User model and I want to set different validations for creation process and for update process.
You can see something about what I'm saying in the following example:

# app/models/user.rb

class User
  include MotionModel::Model
  include MotionModel::ArrayModelAdapter
  include MotionModel::Validatable

  columns :external_id, :email, :password, :password_confirmation

  validate :email, presence: true, email: true
  validate :password, presence: true, if: :new_user?
  validate :password_confirmation, confirmation: true, if: :new_user?

  def new_user?
    external_id.nil?
  end
end

# app/screens/signup.rb

# (...)
u = User.new(email: '[email protected]', password: 'secret', password_confirmation: 'secret')
if u.save
  # do successful stuff
else
  # do failure stuff
end
# (...)

[sxross]

It looks like you are doing a send for the :if unless I've misunderstood your code. This is air-code below, but see if this handles the two cases.

if validation[:if]
  case validation[:if]
    when Symbol then return send(validation[:if])
    when Proc then return call(validation[:if])
    else
      raise ArgumentError.new(':if requires a Symbol denoting a method or a Proc/lambda')
    end
  end
end

Note that the validator is an instance method of the model, so you would be able to write code like this:

validate :password, if: -> { password.length > 7 && password.match(/[0-9]/ && new_user? }

# or

validate :password, if: :strong_password?

# ...

def strong_password?
  # some code to really figure out password strength
end

What do you think? Would something like this work?

[aviscasillas]

You are right, it should work. Let me check it out and I'll come back with some changes 😉
Just one comment on your example. I think that maybe the strong_password? method wouldn't be a condition, it would be a validation, and you could set this validation under a condition with something like:

validate :password, strong_password: true, if: :have_to_validate_password?

Right?

Thx!

[sxross]

I just used strong_password as an example. You might want to validate that an address has a numeric zip code if it is in the US. So that might be like this:

validate :zip, if: -> {
  case country
    when 'US' return zip.match(/[^0-9]{5}(-[0-9]{4})?/
    else return !zip.empty?
  end
}

Something like that. It's just one other way to write validating code -- moving the method up to the validate macro and not writing a separate method unless there is more than one field that requires the same validation.

[aviscasillas]

Yes, totally agree.

[aviscasillas]

Sorry @sxross, I was thinking on it and I'm not "totally agree" with you.

• My point: Use :if to define conditions on when the validation must be executed (rails way).
• Your point: Use :if to define a custom validation (not the rails way).

And I think that two scopes for the same option is not correct.
I think your point could be good in a separate feature. Maybe using another option like :with:

validate :password, with: -> {  password.length > 7 && password.match(/[0-9]/ && new_user? }

What do you think?

[aviscasillas]

@sxross Travis is failing again. I don't understand why, all is working fine in my machine.
Could you refresh Travis to see if the problem persists?

Thx!

[sxross]

I agree. That makes perfect sense.

On Nov 22, 2014, at 3:53 AM, Albert Viscasillas Campanyà [email protected] wrote:

Sorry @sxross https://github.com/sxross, I was thinking on it and I'm not "totally agree" with you.

My point: Use :if to define conditions on when the validation must be executed (rails way).
Your point: Use :if to define a custom validation (not the rails way).
And I think that two scopes for the same option is not correct.
I think your point could be good in a separate feature. Maybe using another option like :with:

validate :password, with: -> { password.length > 7 && password.match(/[0-9]/ && new_user? }
What do you think?

—
Reply to this email directly or view it on GitHub #128 (comment).

[sxross]

Please try removing rake from the Gemfile. See if that helps.

[aviscasillas]

@sxross I've made it working doing some changes in Travis configuration and gem dependencies.
Can you review the last commit to check that's all right?