One gripe I have with ActiveRecord is that the validation normally kicks in only when the entity is persisted or updated. This means your -- possibly invalid -- domain object goes through the web layer and your business logic until it gets caught by the validation framework. I prefer the XWork/WebWork approach where the validation mechanisms can be context sensitive, and always apply immediately when the input data reaches the controller.

Cedric: It's actually quite easy to bundle all this up in either a mixin or your own meta validation. You could wrap it up into something like validates_cedricness_of :name and have that include both length, uniqueness, and format. Zsolt: You can just call model.valid? to do this.

Zsolt, You can manually invoke validation whenever you like by calling valid?

Cool :)

Great, thanks David!

For a system with a lot of GUIs, you really need to have a generic mechanism to transfer data back and forth anyway. You really should define that mechanism with meta data. At least an XML template listing the objects/attributes rather than just throw a hashtable out there. With those requirements identified, adding a simple drop-in validation into the XML definition should be pretty easy. Just specify the name of the class used to validate the field and an optional string parameter. It certainly makes more sense than specifying the validation relationship in code anywhere. This would allow you to specify much more than validations too, you could identify what to do with the data when it connects with any other sub-system. Oh well, that's how I was designing it anyway.

XML SUCKS! Keep your horrid metadata away from rails! Mixins can keep rails models much nicer, and keep the application simple.

There's nothing wrong with the code if you don't want to reuse it though ;-) Thanks for the reference to my blog, nice to see folks are reading it. If I reach a point where I need to validate a name the same way in other parts of the code that would violate the DRY principle I like DHH's suggestion.

Well, you don't just call valid() on an object to validate it, no, you ask the validation framework to validate the object: ActionValidatorManager.validate(object, context); But, as you do in Ruby, we could add this as a mixin using AOP to any objects we like to have the validation framework validate them. One question for the Rails folks... How do you do context-sensitive validations? Also, how do you collect the validation error messages, and how do you localize them? These are all requirements that my validation framework (the XWork Validation Framework) had to address for real-world requirements at work.

I really like the Mixin idea. You can then break out all your common validation rules into a set of declarative classes, and mixin as needed. Kind of like meta-data validation rules, but its not metadata. Nice. Three cheers for mixins.

What you need to do is Mixin with AOP then Inject with IoC, squeeze in a Context, implement IValidatable and finally let it sit overnite. wallah !!!

We have not had a need to do context-sensitive validations and I'd argue that most applications do not. So the the validation rules that you specify in the Rails models are the absolutes, the "must always be true" kind of validations. If you have context-sensitive validations needed on top of that, you'll have to roll on your own. So this is one of those "most people, most of the time" things. We're not after the "all people, all of the time" kind of framework coverage.

[quote] We have not had a need to do context-sensitive validations and I'd argue that most applications do not. So the the validation rules that you specify in the Rails models are the absolutes, the "must always be true" kind of validations. If you have context-sensitive validations needed on top of that, you'll have to roll on your own. So this is one of those "most people, most of the time" things. We're not after the "all people, all of the time" kind of framework coverage. [/quote] hmm, well look at the first post in this thread. There is a real use case for the need of it. What I like in XWork/WW approach (same goes for Spring with its rules validations) even more is that I can run the same validation in multiple layers presentation and business, and if my business and presentation sit on the same JVM I can propagate validation that was done already into the business layer so it does not waste its time re-checking. He, he no need for context sensitive validation --> you must be kidding me.

[quote] We have not had a need to do context-sensitive validations and I'd argue that most applications do not. So the the validation rules that you specify in the Rails models are the absolutes, the "must always be true" kind of validations. If you have context-sensitive validations needed on top of that, you'll have to roll on your own. So this is one of those "most people, most of the time" things. We're not after the "all people, all of the time" kind of framework coverage. [/quote] hmm, well look at the first post in this thread. There is a real use case for the need of it. What I like in XWork/WW approach (same goes for Spring with its rules validations) even more is that I can run the same validation in multiple layers presentation and business, and if my business and presentation sit on the same JVM I can propagate validation that was done already into the business layer so it does not waste its time re-checking. He, he no need for context sensitive validation --> you must be kidding me.

Ref: Contextual validation use cases I think this is mis-named to be honest (and getting lots of google hits for the wrong thing). I would call this multi-layer validation and the great thing about RoR is the fact that it isn't clunky like Spring and other Java frameworks I have worked with (I have had 8-9 years of professional Java experience and 2 year of Python and Ruby, so I am not just a Ruby head or anti-Java head). In fact, even Marc Fluery of JBoss (a big Java head) agrees that keeping your apps as thin and stateless as possible is best for scaling apps to handle significant load. You may or may not like his arrogant way, but I think in this instance he makes a genuinely great point. Why uber-architects insist on having multiple seperate containers for their apps unless extremely domain-specific use cases mandate this is beyond me. I have worked with plenty of uber-architects that want to redesign the world to make it even more generic than the vast majority of real world use cases need them to be and ALL of those projects have been complete failures. Of course, the opposite extreme also produces project failures. However, if we agree that RoR's main focus is on helping application developers build streamlined web applications and that Marc Fluery has a good point, then I would argue that this is a moot point. But if you like Spring so much, stick to it, please! As for those that are interested in doing what I would call context-sensitive validation... RoR provides the validate, validate_on_create and validate_on_update protected methods for application developers to override them. This seems like the perfect place to do contextual validation.

how to perform email validation i m confused when i m using following coe it return code it not consider index('') method of ruby in model. mymodwl.rb def validate apos=:email.index('@').to_i dotpos=:email.rindex(".") lastpos=:email.length-1; if (apos 3 || lastpos-dotpos<2) errors.add(:email, "is missing or invalid") end end

apos=:email.index(/@/).to_i use this code

i have make upload image form, i save path info about image on database and i placed uploaded image to public/images/user_pix/ directory everything is running well, except i can't validate content type of image, my apps accept jpg,gif & png filetype only so guys, would you please tell me how to validate content type when you save/update image data *i'm sorry if my english bad

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In my address model, I have address line 1 and address line 2. Address line 2 is optional and I want to validate it when present. So, I defined the following validate function. def validate if(!address_line_2.nil? and !address_line_2.blank?) validates_length_of :address_line_2, :maximum => 30, :too_long => " exceeds %d characters" validates_format_of :address_line_2, :with => /^(\w+|(\s|,|-|\.|')*)+$/ return true end end But rails throws a NoMethodFound exception for validates_length_of. How can I fix it?

OK. I solved it as follows: validates_length_of :address_line_2, :maximum => 30, :too_long => " exceeds %d characters", :if => Proc.new { |a| !a.addres s_line_2.blank? } validates_format_of :address_line_2, :with => /^(\w+|(\s|,|-|\.|')*)+$/, :if => Proc.new { |a| !a.address_line_2.blank? } But I still would like to know the cause for the NoMethodFound error in the previous approach. Thanks.

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