What is Layout and what is View in ZF? When and wh

问题:

I can't understand when to use Layout's variables and when to use View's variables to get page segments on the page. Here is the picture form their Layout package tutorial ($this means the View instance everywhere):

Why Navigation, Content and Sidebar segments are got as Layout variables?

$this->layout()->nav;

But HeadTitle, HeadScript, HeadStylesheet are got straightly from View?

$this->headTitle(); // I know that this is a placeholder view helper. 
                    // But this segment of the page logically belongs to Layout.
                    // and it has to be called smth like view->layout->placeholder 

And why Header and Footer are from some partial method of the View but not Layout's properties?

$this->partial('header.phtml');

I've tried to change them and both ways work fine:

echo $this->nav; // I assigned navigation segment script to the View and it works;

I tried to assign Footer segment script to the Layout and it also works:

$layout->footer = $footer;
echo $this->layout()->footer;  // it also works, it's displayed on the page

Any of the ways may be applied to any variable on the page. For example in Navigation segment I have a lot of variables to display and I can output them using both ways - one variable as Layout's property, another one sa View's property.

So what is the rule to use them right way? When should I use View's variables and when Layout's ones?

回答1:

I agree that this isn't very clear from the documentation, and I don't think $this->layout()->nav is explained at all. A few points that might help:

• $this->layout() is actually a call to the layout view helper, which returns the current instance of Zend_Layout.
• Zend_Layout registers its own placeholder helper (with the key 'Zend_Layout'), and by default creates a 'content' variable in this.
• the Zend_Layout class has a magic __get() method which proxies any member variable calls over to its registered placeholder container. So calling $this->layout()->content is another way of writing $this->placeholder('Zend_Layout')->content
• the Zend_Layout class also has a magic __set() method that proxies stored data to the placeholder class. So $layout->footer = 'foo' is the same as calling $this->placeholder('Zend_Layout')->footer = 'foo' in the view

With that in mind:

Why Navigation, Content and Sidebar segments are got as Layout variables?

As these are accessing data stored in Zend_Layout's placeholder. You could also use $this->placeholder('Zend_Layout')->content

But HeadTitle, HeadScript, HeadStylesheet are got straightly from View?

These are view helpers.

And why Header and Footer are from some partial method of the View but not Layout's properties?

This is the standard way of accessing content from other templates.

In general, assume that using the view object is the correct way to access the data. Use the layout object/helper only if you know the data is in the layout placeholder.

The advantage of using placeholders over partials is that you can access and modify them in several different places, including in the view itself. For example say you had a sidebar which is stored in a partial. If you were to store this in the Zend_Layout placeholder instead (for example in a controller plugin), you can then override this for certain actions in the controller:

public function someAction()
{
    $this->view->layout()->sidebar = 'Some other sidebar content';
}

or in the view script itself:

<?php $this->layout()->sidebar = 'Content for this page only'; ?>