What's the difference between Partial and Slot in Symfony?

Question

The two concepts Partial and Slot seem the same for me. Both of these two features replace placeholders in template with actual markup.

When should I use Partial and when should I use Slot?

Answer 1

The major difference between slots and partials is that the rendering for a given slot resides within a certain template. In opposite, the partial is merely an include of a template into another template.

"Basically, a slot is a placeholder that you can put in any of the view elements (in the layout, a template, or a partial). Filling this placeholder is just like setting a variable. The filling code is stored globally in the response, so you can define it anywhere (in the layout, a template, or a partial). Just make sure to define a slot before including it, and remember that the layout is executed after the template (this is the decoration process), and the partials are executed when they are called in a template."

Examples of ways of using each are:

• Title for your page - would probably be placed in a slot (or in the title helper), and you would then in your layout check whether the slot was defined and then show it.
• Sidebar items - say you have 3 sidebar "slots", you would then have three slots, for example 'sidebar-1', 'sidebar-2' and 'sidebar-3'. In your template you would then define the slot, which could be rendered using a partial (or even a component) if you wanted.

I hope that clarified it a bit.

Answer 2

A partial comes from a file:

include_partial('thing', $params) will include _thing.php with $params in it's scope.

Slots are not files, but set somewhere else in the template/controller:

slot('title', 'Home Page');
echo '<title>'.slot('title').'</title>'

Answer 3

All you need to know is the Symfony cheat sheet View. Partials, components, slots and component slots (PDF, 45 KB).

Answer 4

You could think of a slot as an OO method definition. Your layout defines slots. The template extends the layout and fills those slots (by overwriting the methods). You can also have a default content for a slot, which is displayed when it's not overwritten.

Partials on the other hand would be like composition. They are a reusable component that templates can access. Roughly they are the equivalent of a simple include statement, but you pass in the variables it uses.

This page does a pretty good job at explaining the concepts: http://www.symfony-project.org/book/1_2/07-Inside-the-View-Layer