What Model Data Is Available On Edit

Question

I have created a custom module with my own db table. My question is; what data is available to me in the block class while I'm editing an entry?

For example, I use the products collection in my block and call it as follows:

$collection = Mage::getModel('catalog/product')
                    ->getCollection()
                    ->addAttributeToSelect('*');

Now, I can use the getters to retrieve info, such as:

$collection->getEmail();
$collection->getFirstname();
... etc, etc

All good. Now, if my custom model is called test_model/test, and I have an instance like so:

$test = Mage::getModel('test_model/test');

Calling a getter for getMyfield(); produces nothing. Obviously, if I explicitly load an item:

$test = Mage::getModel('test_model/test')->load('1');

Then I do have those getters available.

So... what am I missing? Why do I have to load the row I want first? Shouldn't it be available on edit with $this->getMyfield();.

Help a Mage nooby out, please.

Answer 1

If you use Mage::getModel('some/model') method Magento only returns model class without values.
If you use Mage::getModel('some/model')->load($id) then Magento loads the object (one row) from db table and returns this object with it's values. And you can get some value via $model->getMyField(). Also you can define some methods and default values for model class:

class My_SomeModule_Model_SomeModel extends Mage_Core_Model_Abstract{
    protected function _construct()
    {
        $this->_init('somemodule/somemodel');
    }
    public function getSomeValue(){
        //here is your some logic to calculate or load some $value
        return $value; 
    }
    public function validate(){
        //you can write object values validation logic  
        return $this->getMyField()!==null;
    }
    protected function _beforeSave(){
        if(!$this->validate()){
           throw new Exception('Some validation Message here');
        }
        return parent::_beforeSave();
    }
}

Using model:

$model=Mage::getModel('somemodule/somemodel')->load($id);
$model->setMyField($model->getSomeValue());
$model->setAnotherField('some value');
$model->save();