Some thoughts on Constraints

[Dan Vega]

Since the idea to set constraints in the model came from grails I have been looking at a lot of their constraints and I wanted to pick your brains on a few things. In this release you are going to have the ability to define constraints like so

component persistent="true" table="Users" extends="BaseEntity" {

property name="id" column="user_id";

property name="firstName";

property name="lastName";

property name="email";

property name="age";

property name="username";

property name="password";

property name="passwordConfirm" persistent="false";

property name="type";

property name="roles" fieldtype="many-to-many" cfc="Role" singularname="role" fkcolumn="user_id" inversejoincolumn="role_id" linktable="users_roles";   

// model constraints

this.constraints = [

{property="firstName",blank=false},

{property="lastName",blank=false},

{property="email",blank=false,email=true,unique=true,context="create,foo,bar"},

{property="age",blank=false,size="18..30"},

{property="passwordConfirm",blank=false,validator="passwordsMatch"},

{property="type",blank=false,inList="employee,manager"}

];

public User function init(){

return this;

}

// custom validators

public boolean function passwordsMatch(){

if( getPassword() == getPasswordConfirm() ){

return true;

}

return false;

}

}

Some real questions came up while I started writing the constraints. 

1.) With a restraint like blank=false you are telling hyrule that you do not want to allow a blank value. 

     a) should this be a string only or check for a blank on any value (empty collection/empty array)

     b) would a user ever say blank=true.. ie should we ever test for that?

2.) Min / Max 

     a.) should min and max only test numbers or all simple values (strings/dates/numbers)

     b.) if so grails has a minSize/maxSize we could do the same to test collection sizes

3.) Same questions with creditcard and email

     a) would a user ever say creditcard=false... why would you ever test to see if something is not a credit card.

4.) I have some implementation questions on unique but I will save that for another thread.

[Tony Nelson]

Here's a random thought completely unrelated to your questions...

If you're defining your constraints through this.constraints = [], you
might run into issues with inheritance, since you can't really inherit
the this scope from a parent class.

While using this.constraints might be more concise, I think I would
prefer to use metadata annotations since then inheritance isn't really
an issue. Plus your objects should serialize a lot cleaner too.

-Tony

[Dan Vega]

You will still be able to use meta data as I planned on supporting both.. 

I totally forgot that this won't inherit and didn't think about out because I wanted to getting working before I worried about inheritance.. 

I am in a bummed out mood now..what to do

[Dan Vega]

I know this is a cop out but if 

Employee extends user

your object instantiation is done at the employee level

+User 

  -first

  -last

+Employee

 -social

Employee cfc

this.constraints = [

 {property="first",blank=false}.

 {property="last",blank=false}.

 {property="social",blank=false,ssn=true}

];

[Dan Vega]

disregard ... I don't like that approach. I seriously don't know how I will be able support this now.. sigh

[Dan Vega]

OK.. How about this, again I want to support 2 ways of defining constraints.. Annotations / Setting Property Constraints via code

this.constraints is not going to work because we have issues with inheritance. What about this approach? 

Person

component persistent="true" {

property name="id" column="person_id" fieldtype="id" generator="increment";

property name="firstName";

property name="lastName";

property name="constraints" persistent="false";

public Person function init(){

return this;

}

public void function setConstraints(){

variables.constraints = [

{property="firstName",blank=false},

{property="lastName",blank=false}

];

} 

public string function getName(){

return getFirstName() & " " & getLastName();

}

}

Employee

component persistent="true" extends="Person" {

property name="employeeid" column="employee_id" fieldtype="id"; 

property name="salary" ormtype="double";

property name="constraints" persistent="false";

this.constraints = [

{property="salary",blank=false}

]; 

 

public Employee function init(){

return this;

} 

public void function setConstraints(){

variables.constraints = [

{property="salary",blank=false}

];

} 

}

[Dan Vega]

That won't work either because you end up with the same issues, no way to get the properties of a parent w/out instantiating an object. I think I am just going to support this 

this.constraints = []

but w/out inheritance, if you need inheritance you will have to use annotations. smh

blog post coming soon