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Hello, and welcome back
to the Pharo course.

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This segment
covers two more aspects.

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I'll cover them in depth.

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You'll use them yourselves
in the TinyBlog exercises.

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First, what web development can we do
once we have described data?

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Second, how does Seaside use REST?

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Seaside is one of the frameworks
for REST in Pharo.

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Let's start with the first subject.

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Magritte is a framework
based on the hypothesis

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that if you describe your data once,

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it can generate several objects
based on this data.

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Webforms and graphic interfaces,
for example.

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In this course, I'll be focusing on

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showing you how to generate
Seaside components

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so that you can code
web applications faster.

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We'll take the class "Address"
as an example.

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These are Swiss addresses.

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An address is defined
as a street, a place,

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a postal code, and a canton.

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I have an instance which describes
a particular street.

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So far, this is just
standard programming.

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Now, what Magritte does

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is describe the fields
in the class.

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It will describe a string in such a way
as to define it as a street name.

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The postal code description
is more interesting.

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First of all, we are going to say

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an address is not valid
without a postal code.

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Addresses lacking postal codes
are invalid.

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And all Swiss postal codes
are figures between 1000 and 9999.

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This is specified
in the NumberDescription.

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This information can be taken
into account

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for automatic form validation.

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For Place, we also describe
it as required, and as place.

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Moreover, in Switzerland,
there are 26 cantons.

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The canton is part of a list,
so we have SingleOptionDescription.

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It is required. We want it to be sorted,
and the options listed.

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So the list of options
is limited to these 26.

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Once that's done,

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what can we do with Magritte?

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Here is how the address
is described in Pharo.

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We'll define a descriptionStreet
as a StringDescription,

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with such and such a label
and priority.

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For street numbers,
I define a NumberDescription:

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I assign a different priority
and label.

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I specify "Required"
and give my minimum and maximum values.

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The very first thing
I can do with this description

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is write a little tiny program
to interpret the address

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and generate reports.

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I take an address,

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and run it through this program,

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which generates a little report:

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The name of the street,

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The place - Bern,
and the canton, Bern.

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Postal code 3012.

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I can use the fact
that my data has been described

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to generate reports.

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That was the simplest kind.

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But now we'll do more complex
things with Seaside,

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like creating a visual component.

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Here, I am saying,

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"Address object, I want to see you
as a component."

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That generates this part.

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I'll add a validation form,
which gives me "Save" and "Cancel."

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And I'll write a "call" command
so it displays.

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As you can see, I managed all that
without even using the Seaside DSL.

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Described, my web components
are generated automatically.

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That's powerful!

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Here is what the company Quuve does

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Quuve is an American
portfolio management platform.

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The whole display
was done with Seaside and Magritte.

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All the reports
are generated automatically.

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That's a serious gain
in productivity!

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The idea of this course
is to give you some intuition

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of what can be done
when you describe your data,

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especially
with web component generation.

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You'll do that in TinyBlog.

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Now, I'll show you the potential
in Seaside's REST layer.

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It enables client-server communication
in the absence of visual components.

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REST is integrated into Seaside
smoothly.

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Domain objects will be annotated.

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You'll have a natural conversion
between URL parameters

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and SmallTalk or Pharo methods.

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To give you an idea of the complexity,

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we'll define what we call a "filter":

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TinyBlog Restful Filter.

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is a subclass of WARestful -
it doesn't matter.

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The important part is the filter I add
down here when I create my application.

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You'll see it in the exercise.

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Now, let's imagine
that I want to get all the blogs

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that I have on my TinyBlog server.

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Here's how:

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First, I define a method

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in the RestfulFilter class,
a method called listAll.

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It corresponds to the anchor
I'm going to use:

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I tell it to use its "get"
from the REST protocol

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to generate text in json form.

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I create a Pharo string stream

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I want the stream to contain
all available blogs.

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I'll take each blog -
and you see another iterator -

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Take each blog
and convert it to Javascript,

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separated by commas.

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That gives me what I want.

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Now we want to do something
a little more advanced.

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Say I want to find a blog
by searching for a title match.

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Here, I can use "post," for example.

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I'll say I want this blog post,
by giving the title next to it.

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I do that by defining a "post" method
that takes a title as a parameter

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along with the "path" concept.

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I tell it, when the URL
contains http..., post/

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and something here,
those characters are the title.

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That's what we see here,
inside the wavy brackets.

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Likewise, I tell it,
that will produce text in json form.

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Then what I do is call upon
TinyBlog functionalities.

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I ask, do you have a post
with a title specified as a parameter?

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Yes? If it's empty, I return an error.

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Otherwise, I put it in my stream
and render my stream.

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There are lots of things
we can do.

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If I want to do a search,
it's the same thing.

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In my URL line, I type

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"search: title" with a value,
it will be matched automatically.

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My title will appear here.

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That's how you work with REST
in Seaside.

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You can have your graphic components
in Seaside

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and a way to expose
your domain functionalities

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with a REST API.

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I've only shown you "gets."

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But all the other REST functionalities
are available:

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Delete, Post, Get, etc.

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I also showed you how Seaside,
paired with Magritte,

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generates powerful forms,
automatically.

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And REST is well integrated.

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Often, people use Teapot
as a REST solution, as well.

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It's a Zinc overlayer
for doing REST prototypes.

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It's a quick way to find out
if their REST API is working.

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Have fun with it.

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There's documentation
in the Web Enterprise Book.