Akelos has a number of methods and different approaches to facilitate [[Validations]] of your [[active-record|ActiveRecord]] model.

===== Overview =====


==== Why validate? ====

Validation is a useful tool to ensure the integrity of information in the database. It forms a minimum standard that all records must meet before they can be saved.

**A valid user example:** 

  * has a name and password
  * has a unique name
  * has a password that is between 5 and 15 characters long

With those rules (except written in real PHP) as part of your model, Akelos will not save any user that doesn't meet the requirements.

When using validation, Akelos keeps track of any validation errors and will build error messages for those errors. It is then useful to display these messages back to the user so the errors may be corrected.

==== When does validation take place? ====

Validation takes place **before a model is saved**. If the model being saved doesn't meet its validation requirements, it will NOT be saved to the database. Attempts to //save// an invalid model return false. This allows for the "if-save" convention: 

<code php>
if($User->save()){
  // user was valid and saved
}else{
  // user was invalid, not saved
}
</code>

You can trigger validation //manually// by calling the models //validate// method.

<code php>
$User->validate();
</code>

But likely more useful would be to call //isValid()//, which runs @validate@ then returns true or false.

<code php>
if ($User->isValid()){
}
</code>

==== Avoiding validation ====


You can skip validation by passing //false// to //save()//.

<code php>$User->save(false);</code>

The method //updateAttribute()// does not trigger validation, and as such, methods that call //updateAttributes()// (//toggleAttribute()//, //incrementAttribute()// and //decrementAttribute()//) do not trigger validation either.

Skipping validation may result (obviously) in invalid data being recorded to the database.


==== What happens when a model is validated? ====

When a model is validated, any validation errors will be collected in the models //_errors// array.


===== More information =====

  * [[how-to-validate|How to validate]]
  * [[http://api.akelos.org/ActiveRecord/Base/AkActiveRecord.html#methodvalidate|Validation API Documentation]] has all sorts of details about what methods are available.