Filtering Meta Programming - No Frills Magento Layout. Alan Storm

If you follow the inheritance chain of the Template Filter far enough back, you

eventually reach

Varien Filter Template

M a g e _ W i d g e t _ M o d e l _ T e m p l a t e _ F i l t e r e x t e n d s M a g e _ C m s _ M o d e l _ T e m p l a t e _ F i l t e r e x t e n d s M a g e _ C o r e _ M o d e l _ E m a i l _ T e m p l a t e _ F i l t e r e x t e n d s M a g e _ C o r e _ M o d e l _ E m a i l _ T e m p l a t e _ F i l t e r e x t e n d s V a r i e n _ F i l t e r _ T e m p l a t e

1. Look for any

style strings

2. Parse the token for the directive name (

foo

above)

3. Create a method name based on the directive name. In the above exam-

ple, the directive name is

foo

, which means the method name would be

fooDirective

4. Use

call user func

to call this method on itself, passing in the an array

containing a tokenized version of the directive string.

It’s beyond the scope of this book to cover the implementation details of each

specific directive. We mention mainly to let you know that, if you’re trying to

debug a particular template directive, say

you can find its implementation method by taking the directive name (

media

),

and adding the word

Directive

. A quick search through the code base should

turn up the implementation

# F i l e : a p p / c o d e / c o r e / M a g e / C o r e / M o d e l / E m a i l / T e m p l a t e / F i l t e r . p h p p u b l i c f u n c t i o n m e d i a D i r e c t i v e ( $ c o n s t r u c t i o n ) { $ p a r a m s = $this - > _ g e t I n c l u d e P a r a m e t e r s ( $ c o n s t r u c t i o n [ 2 ] ) ; r e t u r n M a g e :: g e t B a s e U r l ( ’ m e d i a ’ ) . $ p a r a m s [ ’ url ’ ]; }

In this specific case we can see that the

{{media ...}

directive simply grabs the

base media URL using

Mage::getBaseUrl(’media’)

, and appends the

url

parameter

to it.

Visit http://www.pulsestorm.net/nofrills-layout-chapter-six to join the discus-

sion online.

Widgets

Consder the following situation. You’re a developer. You have a deep knowledge

of the Magento system. The corporate VP in charge of giving you things to do

runs into your work area and says

I want to add a YouTube video to the sidebar?!

You start explaining layouts, and blocks, and pages, and how they render, and

which XML file he’ll need to edit, or maybe you could add it as a page update

o...

Your boss then gives you that steely, bossy look and says again

I wantto add a YouTube video to the sidebar

Most people don’t work on their own cars. Most people don’t harvest or hunt

their own food. And most people don’t want to code their own websites. That’s

the problem widgets set out to solve. In this chapter we’ll give you a full overfull

of the Magento widget system. From using the widgets that ship with Magento,

to creating your own widgets, to understanding how widgets are inserted into

the flow of the Layout.

7.1 Widgets Overview

So, what are widgets?

1. Widgets are Magento Template Blocks

2. Widgets Contain Structured Data

3. Widgets Contain Rules for Building User Interfaces

5. Widgets contain rules that say which blocks in the layout system are

allowed to contain them

Let’s start by building ourselves a minimum viable widget, and inserting it into

a CMS page. We’ll be building our widget in the

Nofrills Booklayout

module.

You, of course, are free to add widgets toanymodule you create.

To start with, we need to create a configuration file that will let Magento know

about our widget. Being a newer subsystem of Magento, widgets have their

own custom XML config file which will be merged with the Magento config as

needed. Widget config file are named

widget.xml

, and should be placed in your

module’s

etc

folder

<! - - # F i l e : a p p / c o d e / l o c a l / N o f r i l l s / B o o k l a y o u t / e t c / w i d g e t . x m l - - >

< widgets > </ widgets >

There are times where Magento will load the widget config from cache, and

there’s other times where the config will always be loaded from disk. Because

of that, it’s best to always clear the cache when making changes to this file.

We now have an empty widget config. Next, let’s add a node to hold our widget

definition

<! - - # F i l e : a p p / c o d e / l o c a l / N o f r i l l s / B o o k l a y o u t / e t c / w i d g e t . x m l - - >

< widgets >

< n o f r i l l s _ l a y o u t b o o k _ y o u t u b e t y p e = " n o f r i l l s _ b o o k l a y o u t / y o u t u b e " > < name > Y o u T u b e E x a m p l e Widget </ name >

< d e s c r i p t i o n t y p e = " d e s c " >

T h i s w i g e t d i s p l a y s a Y o u T u b e v i d e o . </ d e s c r i p t i o n >

</ n o f r i l l s _ l a y o u t b o o k _ y o u t u b e > </ widgets >

Each second level node in this file tells Magento about a single widget that’s

available to the system. You should take steps to ensure this node’s name is

unique to avoid possible collisions with other widgets that are loaded in the

system from other modules. In this case, the name

nofrills layoutbook youtube

should suffice.

It’s the

type="nofrills booklayout/youtube"

attribute we’re interested in. This de-

fines a block class alias for our widget. We’re telling Magento that the block

class

N o f r i l l s _ B o o k l a y o u t _ B l o c k _ Y o u t u b e

should be used for rendering this widget. The

<name/>

and

are used for text display in the Magento Admin Console.

Let’s create that class. Add the following file

# F i l e : a p p / c o d e / l o c a l / N o f r i l l s / B o o k l a y o u t / B l o c k / Y o u t u b e . p h p

<? php

i m p l e m e n t s M a g e _ W i d g e t _ B l o c k _ I n t e r f a c e { p r o t e c t e d f u n c t i o n _ t o H t m l () { r e t u r n ’ < o b j e c t w i d t h = " 6 4 0 " h e i g h t ="505" > < p a r a m n a m e =" m o v i e "

v a l u e =" h t t p :// www . y o u t u b e . com / v / d Q w 4 w 9 W g X c Q ? fs =1& amp ; hl = e n _ U S " > </ param >

< p a r a m n a m e =" a l l o w F u l l S c r e e n " v a l u e =" t r u e " > </ param > < p a r a m n a m e =" a l l o w s c r i p t a c c e s s " v a l u e =" a l w a y s " > </ param >

< e m b e d src =" h t t p :// www . y o u t u b e . com / v / d Q w 4 w 9 W g X c Q ? fs =1& amp ; hl = e n _ U S " t y p e =" a p p l i c a t i o n / x - s h o c k w a v e - f l a s h "

a l l o w s c r i p t a c c e s s =" a l w a y s " a l l o w f u l l s c r e e n =" t r u e " w i d t h = " 6 4 0 " h e i g h t ="505" > </ embed > </ object > ’ ; }

}

This class ismostlya standard block class. It extends from the

Mage Core Block Abstract

class, and we’ve overridden the base

toHtml

method to have this block return

the embed code for a specific YouTube video. The one difference you’ll notice

is the class definition also has this

i m p l e m e n t s M a g e _ W i d g e t _ B l o c k _ I n t e r f a c e

This line is important. It tells PHP that our class is implementing the widget

interface. If you don’t understand the concept of PHP OOP interfaces, don’t

worry. Just include this line with your widget class. Without it, Magento won’t

be able to fully identify your block as a widget class.

That’s it! We now have a super simple widget. Let’s take it for a spin!

In document No Frills Magento Layout. Alan Storm (Page 97-101)