Question

Basically I have an html form for inserting a product. The field names, as well as the $_POST vars, are initialized in my Product class. The contructor is “listening” for the submit button. When the user submits the form, the object’s state changes to let’s say “Ready”, which means its attributes are initialized and ready to be inserted into the database.

Then I need to return a message depending on the status of insert (Sucess or Failure), If sucess i’ll print something like “Product Inserted Successfully”, if it fails: “Null fields detected”.

My question is if I’m allowed to put this kind of logic in the view? Like this:

<?php $myproduct = new Product(); ?>

<form>
<!-- Fields -->
</form>

<?php
if ($myproduct->ready()) :
    if ($myproduct->insert()) : ?>
        <p>Product inserted successfully</p>
<?php
    else : ?>
        <p>Null fields detected</p>
<?php
    endif;
endif; ?>

I really can’t think of a simpler way, since I really need to show the message depending on the insert() return status.

So is it allowed in the MVC pattern to mix that kind of logic in the view? I’m not exposing any kind of business logic, just checking the object’s status.

Answer 1

No. The domain business logic has no place in the view (nor in the presentation layer as whole). That’s why MVC has the model layer.

When you are submitting a form, the order of operations should be as following:

1. controller receives the request with $_POST data

2. controller sends the information to the model layer

   • if data is valid, model layer saves the information
   • if data is invalid, model layer sets and acquires error state and saves it (usually in session)

3. controller notifies current view that there was POST sent

4. when view is requested to generate response (preferably, not by controller), it sends a Location HTTP header (to prevent double-posting)

5. controller receives new request (with only GET parameter this time)

6. if required, controller adjusts state of model layer and current view

7. view inquires model layer whether it contains error state

   • if there is error state, view requests list of error code from model layer and based on that information chooses, which templates to use to compose a form with “error” messages
   • if there is no error state in model layer, view uses templates to create a “success” message

There would be the order of operations for form submission in Model2 MVC pattern.

Depending on whether you display error messages and/or success messages in the same view as the form itself, the view instance might check the model layer for error state in STEP 4. Then view could decide which Location header to send.

P.S. The interaction with model layer would most likely happens through service.