Video #4 - Blog - Iteration 2

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Web Application Development: Basic Concepts

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University of New Mexico

Web Application Development: Basic Concepts

124 classificações

This is the first course in a Coursera Specialization track involving Web Application Architectures. This course will give you the basic background, terminology and fundamental concepts that you need to understand in order to build modern full stack web applications. A full stack web developer is familiar with each "layer" of the software technologies involved in a web application, including data modeling and database technologies, the web server environment and middleware components, network protocols, the user interface and basic visual design and user interaction concepts. In this course we will learn by doing. We will start by learning the major components of web application architectures, along with the fundamental design patterns and philosophies that are used to organize them. You will build and continually refine a fully functional full-stack web application as we progress through the modules in this course. Along the way you will be exposed to agile software development practices, numerous tools that software engineers are expected to know how to use, and a modern web application development framework. This course is also available in Spanish. To join the Spanish version, visit this page: https://www.coursera.org/learn/apliweb.

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Module #3 - Managing Data

A successful web application provides information t o users that is (1) useful, and also (2) easy to access and understand. This information is often collected from users, as well as from other information sources, and must be stored in a manner that allows it to be manipulated by the web application. The typical app roach is to store this data in a relational database. In this module you will learn some basic concepts associated with modeling the data in a web application, including h ow to specify the relationships between various data entities. We will also investigate ho w to hook a web application up to a back- end data store, along with good design techniques t hat will make it easier to use the data in your web applications by maintaining consistency th roughout the entire web stack.

Active Record Design Pattern - An Overview0:38

Video #1 - Active Record Design - An Overview4:09

Video #2 - Active Record in Rails8:55

Video #3 - Database Migrations6:44

Video #4 - Blog - Iteration 24:31

Conheça os instrutores

Greg Heileman
Professor and Associate Provost
Electrical and Computer Engineering
Manel Martínez-Ramón
Professor
Electrical and Computer Engineering

[MUSIC]

I showed the first iteration of our Blog App to the CEO of Acme Widget works.

The one that allows you to add, post and comments and she was happy with it.

However she did tell me there's one thing she forgot to discuss with us at our first

meeting, so I pulled put the napkin that we wrote on at the last meeting and

showed it to her.

Here's what she wrote.

The CEO forgot to mention during our last meeting that she'd like the name of

authors to appear beside each of their posts.

She'd like the same thing to happen for comments.

I asked her if she wanted users to create accounts and

then we could place the user name beside each of their posts or comments.

And she liked that idea.

So here's what we ended up with.

We're going to put the author name beside the post,

as well as beside each of the comments.

And we're going to do this by using the username.

So we going to need to create a user model.

Based on this feedback, I created a new ERD that includes this user entity.

Notice that I created a one to many relationship between users and posts and

a one to many relationship between users and comments.

That is, one user can have many posts, and many comments.

So, we're going to need to migrate the database in order to include a new table

for users.

We're also going to need to add foreign key attributes to both the post and

comments tables.

Let's created the migrations that take care of these things.

We'll start by generating a scaffold for users.

So, we're going to have a user model with a first name that's a string and

a last name that's a string.

Next, let's create a migration for

adding the foreign key of a user to the post table.

So, I've got add user ID to posts.

And I'm going to go ahead and add on

the next line, user:references.

So this will indicate that this is going to be a foreign key, and so

this created that migration, and I'm going to do the same thing,

for comments, and then I'm going to continue onto the next line so

that's why I'm putting this backslash.

And then I want to type again user:references and

this is going to create these two migrations.

By the way, you don't have to put the user:references on a second

line if you just want to add a space.

And add it to the end of the rails,

generate migration command it'll also work by doing it that way.

Let's take a look at the migrations that were created.

Back in our editor go to db

under migrate you'll see the new migrations are now there.

Here's the one for creating a new user model.

And then we've got one for

adding a reference, adding a foreign key to the post table.

So because I named the migration, add the user id to posts, it knows to use

posts as the table and it knows to use user, and because I said references,

it's going to create an index, and it knows that it's a foreign key.

And we'll see the same thing was done for comments.

The only thing left to do now is to run these migrations and

let's check out the app.

So we'll run rake db migrate, and we see that it created the new table,

as well as adding the attributes to those two tables for posting comments.

Let's make sure the schema setup properly so go to schema.rb and

we'll see now that post, the post table does in fact have this foreign key for

the user ID so does the comment table and that we're creating a user table as well.

Let's take a look at the running app we'll type rails server and

let's look at the open up our browser.

Here's the running app at localhost:3000, and if you type users,

you'll see that we can add new users.

So the user model seems to be hooked up, and functioning, If we go back, to posts.

You'll see that the posts are still there.

Now there is no user listed here and

there is a couple of things one has to take care of in order to make that happen.

First, we are going to have to add more formal associations to our models and

I'll show you how to do that in the very next video.

But we're also going to have to fix up the HTML, the view itself, and

we're going to have to wait until a later module on user interface in order to

show you how to do that.

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