How do you handle data validation in the model using ColdFusion Model-Glue?

MVC best practices state that the model should handle input/data validation. Let's say that we have a model that creates new user accounts, with the following fields and constraints:

Username - not null, not already in DB
Password - not null, alphanumeric only
E-mail - not null, not already in DB, valid e-mail format

We have an AccountModel with a CreateNewUser() function:

component
{
    public void function CreateNewUser(string username, string password, string email)
    {
        // create account
    }
}

Then we have a controller that processes a form post and tells the model to create the account:

component
{
    public void function NewUser()
    {
        var username = event.getValue("username");
        var password = event.getValue("password");
        var email = event.getValue("email");

        var accountModel = new AccountModel();
        accountModel.CreateNewUser(username, password, email);

        event.addResult("UserCreated");
}

Now I want to add validation. If the user fails to provide input for all three fields, the application should show the user three validation error messages. This is easy enough to do in the controller:

// assumes that ValidateInput() is a function on the controller that returns an array
var validationErrors = ValidateInput(username, password, email);

// if there were any validation errors, return a ValidationError result
if (len(validationErrors)
{
    event.setValue("validationerrors", validationErrors);
    event.addResult("ValidationError");
}
else
{
    event.addResult("UserCreated");
}

And the view will pull the validationerrors variable and display the error messages.

However, this logic is supposed to reside in the model. How do I do this? I can think of two ways:

开发者_运维技巧

Method 1: Move ValidateInput() from the controller to the model. Now the controller has to call ValidateInput() first before CreateNewUser(). If the programmer forgets to do this, CreateNewUser() will throw a validation exception. The downside to this is that now every data operation that requires validation will need an if/else block.

Method 2: Forego having to call ValidateInput() and just call CreateNewUser() directly. If there were any validation errors, an exception will be thrown and it will contain the error message array. This method would work in C#, but it looks like ColdFusion does not support returning of data with the exception, only an exception message and type. Also, every data operation will require a try/catch block.

Method 3: ??

How would you handle validation in this case? Is method 1 what most people do when it comes to validation in the model? Or do people typically use method 2? Or is there a method 3 that I'm not thinking of?

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I don't think you should couple the validation of the user's data entry to the creation of the user's account: they are too different things.

If you couple the two together, it means you're basically doing form validation every time you create an account, which doesn't seem right to me.

I see form validation as a UI concern, more than a concern of the objects that might be ultimately created from that data. Obviously your createNewUser() method has its own business rules (which will probably closely mirror that of the validation for a create-new-user form, but they are still separate concerns).

It is possibly a bit unorthodox, but I will put a validateUserData() (or something) method in my User CFC which the form-validation model then calls to help with the validation. This means the business rules for a user are in the same place, and can be called separately. Thereafter, createNewUser() works on a garbage-in/garbage-out principle.

Sidenote: createNewUser() is a bit of a tautological name, innit? What other sort of user would you be creating other than a new one? Also, if it's in your Account.cfc; is it a new user or a new account that's being created? If an account and a user are not synonymous and an account might exist without a user (or vice-versa), perhaps you ought to have a User.cfc too. Then again, this code you've given us could simply be for the purposes of illustration, and you've got all this covered.