How to add a field calculated from another model table in Agile Toolkit?

问题

atk4.2.1

I have two models Invoice and Payment, I want to add a field (expression) in the invoice, I can calculate the already amount paid (it can have several partial payment), I added a join and an expression, dut they don't work, what is the right way to write that expression?

class Model_Invoice extends Model_Table {
    public $table='invoice';
    function init(){
        parent::init();

        $this->hasOne('Customer');
        $this->hasOne('Plan');
        $this->addField('date')->type('date');
        $this->addField('amount')->type('money');
        $this->addField('cancelled')->type('boolean')->defaultValue(false);

        $this->join('payment','id');
        $this->addExpression('amountPaid')->set('sum(payment.amount)')
       //*****above expression is not working*********//
    }
}

.

class Model_Payment extends Model_Table {
    public $table='payment';
    function init(){
        parent::init();

        $this->hasOne('Invoice');
        $this->addField('date')->type('date');
        $this->addField('concept');
        $this->addField('amount')->type('money');
    }
}

I might an expression like this instead:

$this->addExpression('amountPaid')->set('(SELECT sum(amount) FROM payment where invoice_id=**CURRENT ID**)');

But how do I get the CURRENT ID in the Model???

回答1:

Got it! It was somehow documented here: http://agiletoolkit.org/learn/understand/model/intro

This is the right way to do it: Inside Model_Invoice:

    $this->hasMany('Payment');
    $this->addExpression('amountPaid')->set($this->refSQL('Payment')->sum('amount'));

Now I really understood what's the porpuse of hasMany()

来源：https://stackoverflow.com/questions/11572856/how-to-add-a-field-calculated-from-another-model-table-in-agile-toolkit