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391 lines
8.9 KiB
Markdown
391 lines
8.9 KiB
Markdown
## Building a 150 KB web blog in V with 0 dependencies
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Hello,
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In this guide, we'll build a simple web blog in V.
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The benefits of using V for web:
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- A safe, fast, language with the development agility of Python or Ruby and
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the performance of C.
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- Zero dependencies: everything you need for web development comes with the language
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in a 1 MB package.
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- Very small resulting binaries: the blog we'll create in this tutorial is about 150 KB.
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- Easy deployments: a single binary file that even includes the precompiled templates.
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- Runs on the cheapest hardware with minimum footprint: for most apps a $3 instance
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is enough.
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- Fast development without any boilerplate.
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*Please note that V and Vweb are at a very early stage and are changing rapidly.*
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The code is available <a href='https://github.com/vlang/v/tree/master/tutorials/code/blog'>here</a>.
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### Installing V
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```
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wget https://github.com/vlang/v/releases/latest/download/v_linux.zip
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unzip v_linux.zip
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cd v
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sudo ./v symlink
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```
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Now V should be globally available on your system.
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> On macOS use `v_macos.zip`, on Windows - `v_windows.zip`.
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If you use a BSD system, Solaris, Android, or simply want to install V
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from source, follow the simple instructions here:
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https://github.com/vlang/v#installing-v-from-source
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### Creating a new Vweb project
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V projects can be created anywhere and don't need to have a certain structure:
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```bash
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mkdir blog
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cd blog
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touch blog.v
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```
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First, let's create a simple hello world website:
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```v
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// blog.v
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module main
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import vweb
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struct App {
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pub mut:
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vweb vweb.Context
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}
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fn main() {
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vweb.run<App>(8081)
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}
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pub fn (mut app App) index() vweb.Result {
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app.vweb.text('Hello, world from vweb!')
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return vweb.Result{}
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}
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pub fn (app &App) init() {}
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pub fn (app &App) init_once() {}
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```
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Run it with
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```bash
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v run blog.v
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```
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```
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Running a Vweb app on http://localhost:8081 ...
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```
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Vweb helpfully provided a link, open http://localhost:8081/ in your browser:
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<img width=662 src="https://github.com/vlang/v/blob/master/tutorials/img/hello.png?raw=true">
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The `App` struct is an entry point of our web application. If you have experience
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with an MVC web framework, you can think of it as a controller. (Vweb is
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not an MVC framework however.)
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As you can see, there are no routing rules. The `index()` action handles the `/` request by default.
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Vweb often uses convention over configuration and adding a new action requires
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no routing rules either:
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```v oksyntax
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import vweb
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fn (mut app App) time() vweb.Result {
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app.vweb.text(time.now().format())
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return vweb.Result{}
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}
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```
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<img width=662 src="https://github.com/vlang/v/blob/master/tutorials/img/time.png?raw=true">
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>You have to rebuild and restart the website every time you change the code.
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In the future, Vweb will detect changes and recompile the website in the background
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while it's running.
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The `.text(string)` method returns a plain text document with the provided
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text, which isn't frequently used in websites.
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### HTML View
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Let's return an HTML view instead. Create `index.html` in the same directory:
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```html
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<html>
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<head>
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<title>V Blog</title>
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</head>
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<body>
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<b>@message</b>
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<br>
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<img src='https://vlang.io/img/v-logo.png' width=100>
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</body>
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</html>
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```
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and update our `index()` action so that it returns the HTML view we just created:
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```v ignore
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pub fn (mut app App) index() vweb.Result {
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message := 'Hello, world from Vweb!'
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return $vweb.html()
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}
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```
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<img width=662 src="https://github.com/vlang/v/blob/master/tutorials/img/hello_html.png?raw=true">
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Good, now we have an actual HTML page.
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The V template language is similar to C#'s Razor: `@message` prints the value
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of `message`.
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You may notice something unusual: the `message` variable created in the `index()`
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action is automatically available in the view.
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It's another feature of Vweb to reduce the boilerplate in your web apps.
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No need to create view models just to pass data, or use an unsafe and untyped
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alternative, like C#'s `ViewBag["message"]`.
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Making all action variables available in the view may seem crazy,
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but V is a language with pure functions by default, and you won't be able
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to modify any data from a view. `<b>@foo.bar()</b>` will only work if the `bar()` method
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doesn't modify `foo`.
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The HTML template is compiled to V during the compilation of the website,
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that's done by the `$vweb.html()` line.
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(`$` always means compile time actions in V.) offering the following benefits:
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- Great performance, since the templates don't need to be compiled
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on every request, like in almost every major web framework.
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- Easier deployment, since all your HTML templates are compiled
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into a single binary file together with the web application itself.
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- All errors in the templates are guaranteed to be caught during compilation.
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### Fetching data with V ORM
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Now let's display some articles!
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We'll be using V's builtin ORM and a SQLite database.
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(V ORM will also support MySQL, Postgre, and SQL Server soon.)
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Create a SQLite file with the schema:
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```sql
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drop table if exists Article;
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create table Article (
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id integer primary key,
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title text default "",
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text text default ""
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);
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insert into Article (title, text) values (
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"Hello, world!",
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"V is great."
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);
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insert into Article (title, text) values (
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"Second post.",
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"Hm... what should I write about?"
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);
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```
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Run the file with `sqlite3 blog.db < blog.sqlite`.
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Add a SQLite handle to `App`:
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```v oksyntax
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import sqlite
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import vweb
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struct App {
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pub mut:
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vweb vweb.Context
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db sqlite.DB
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}
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```
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Modify the `init_once()` method we created earlier to connect to a database:
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```v oksyntax
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pub fn (mut app App) init_once() {
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db := sqlite.connect(':memory:') or { panic(err) }
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db.exec('create table `Article` (id integer primary key, title text default "", text text default "")')
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db.exec('insert into Article (title, text) values ("Hello, world!", "V is great.")')
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db.exec('insert into Article (title, text) values ("Second post.", "Hm... what should I write about?")')
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app.db = db
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}
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```
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Code in the `init_once()` function is run only once during app's startup, so we are going
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to have one DB connection for all requests.
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Create a new file `article.v`:
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```v oksyntax
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// article.v
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module main
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struct Article {
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id int
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title string
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text string
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}
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pub fn (app &App) find_all_articles() []Article {
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return sql app.db {
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select from Article
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}
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}
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```
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Let's fetch the articles in the `index()` action:
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```v ignore
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pub fn (app &App) index() vweb.Result {
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articles := app.find_all_articles()
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return $vweb.html()
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}
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```
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Finally, let's update our view:
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```html
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<body>
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@for article in articles
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<div>
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<b>@article.title</b> <br>
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@article.text
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</div>
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@end
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</body>
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```
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```bash
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v run .
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```
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<img width=662 src="https://github.com/vlang/v/blob/master/tutorials/img/articles1.png?raw=true">
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That was very simple, wasn't it?
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The built-in V ORM uses a syntax very similar to SQL. The queries are built with V.
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For example, if we only wanted to find articles with ids between 100 and 200, we'd do:
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```v oksyntax
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return sql app.db {
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select from Article where id >= 100 && id <= 200
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}
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```
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Retrieving a single article is very simple:
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```v oksyntax
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pub fn (app &App) retrieve_article() ?Article {
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return sql app.db {
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select from Article limit 1
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}
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}
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```
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V ORM uses V's optionals for single values, which is very useful, since
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bad queries will always be handled by the developer:
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```v oksyntax
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article := app.retrieve_article(10) or {
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app.vweb.text('Article not found')
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return
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}
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```
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### Adding new articles
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Create `new.html`:
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```html
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<html>
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<head>
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<title>V Blog</title>
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</head>
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<body>
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<form action='/new_article' method='post'>
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<input type='text' placeholder='Title' name='title'> <br>
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<textarea placeholder='Text' name='text'></textarea>
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<input type='submit'>
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</form>
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</body>
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</html>
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```
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```v oksyntax
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import vweb
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pub fn (mut app App) new_article() vweb.Result {
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title := app.vweb.form['title']
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text := app.vweb.form['text']
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if title == '' || text == '' {
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app.vweb.text('Empty text/title')
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return vweb.Result{}
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}
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article := Article{
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title: title
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text: text
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}
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println(article)
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sql app.db {
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insert article into Article
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}
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app.vweb.redirect('/')
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return vweb.Result{}
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}
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```
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> Untyped `form['key']` is temporary. Very soon Vweb will accept query and form
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parameters via function arguments: `new_article(title, text string) {`.
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We need to update `index.html` to add a link to the "new article" page:
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```html
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<a href='/new'>New article</a>
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```
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### JSON endpoints
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This tutorial used the traditional server-side rendering. If you prefer
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to render everything on the client or need an API, creating JSON endpoints
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in V is very simple:
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```v oksyntax
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import vweb
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pub fn (mut app App) articles() vweb.Result {
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articles := app.find_all_articles()
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app.vweb.json(json.encode(articles))
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return vweb.Result{}
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}
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```
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<img width=662 src="https://github.com/vlang/v/blob/master/tutorials/img/articles_json.png?raw=true">
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To be continued...
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For an example of a more sophisticated web app written in V, check out Vorum: https://github.com/vlang/vorum
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