Symfony 筆記 (3): MVC Demo
Sunday, May 25th, 2008Model-view-controller (MVC) is an architectural pattern used in software engineering. Successful use of the pattern isolates business logic from user interface considerations, resulting in an application where it is easier to modify either the visual appearance of the application or the underlying business rules without affecting the other. In MVC, the Model represents the information (the data) of the application and the business rules used to manipulate the data, the View corresponds to elements of the user interface such as text, checkbox items, and so forth, and the Controller manages details involving the communication to the model of user actions such as keystrokes and mouse movements.
在 Symfony 裡面不用 MVC 來寫程式的話那就完全沒有意義。Model 是資料庫的 Layer，View 是 Template Layer，而 Controller 則是運算 Layer。雖然這些觀念不會太難，但是實際上要把舊有的程式分開還是得仔細想想。下面是書裡面的一段 Demo，算是很好的示範。
Flat PHP File
這種大概是最古老的寫作方式，把所有的程式邏輯與資料庫存取通通包在同一個檔案裡面，HTML 和 PHP 還有 SQL 通通混在一起不但不好修改，而且要維護也比較上多很難。
<?php
// Connecting, selecting database
$link = mysql_connect('localhost', 'myuser', 'mypassword');
mysql_select_db('blog_db', $link);
// Performing SQL query
$result = mysql_query('SELECT date, title FROM post', $link);
?>
<html>
<head>
<title>List of Posts</title>
</head>
<body>
<h1>List of Posts</h1>
<table>
<tr><th>Date</th><th>Title</th></tr>
<?php
// Printing results in HTML
while ($row = mysql_fetch_array($result, MYSQL_ASSOC))
{
echo "\t<tr>\n";
printf("\t\t<td> %s </td>\n", $row['date']);
printf("\t\t<td> %s </td>\n", $row['title']);
echo "\t</tr>\n";
}
?>
</table>
</body>
</html>
<?php
// Closing connection
mysql_close($link);
?>
MVC - Model
Model 是 Database 的 Abstraction。這裡是一段小 demo，實際上 Symfony 使用的是 Propel，大部分的 accessor method 都會自動生出來。
<?php
function open_connection($host, $user, $password)
{
return mysql_connect($host, $user, $password);
}
function close_connection($link)
{
mysql_close($link);
}
function query_database($query, $database, $link)
{
mysql_select_db($database, $link);
return mysql_query($query, $link);
}
function fetch_results($result)
{
return mysql_fetch_array($result, MYSQL_ASSOC);
}
function getAllPosts()
{
// Connecting to database
$link = open_connection('localhost', 'myuser', 'mypassword');
// Performing SQL query
$result = query_database('SELECT date, title FROM post', 'blog_db', $link);
// Filling up the array
$posts = array();
while ($row = fetch_results($result))
{
$posts[] = $row;
}
// Closing connection
close_connection($link);
return $posts;
}
?>
MVC - Controller
Controller 是邏輯的部份。這個 demo 需要用到的邏輯根本沒有，就只是 “從資料庫裡面找出所有 post” 而已，所以基本上只有一行。
<?php
// Requiring the model
require_once('model.php');
// Retrieving the list of posts
$posts = getAllPosts();
// Requiring the view
require('view.php');
?>
MVC - View (Template)
Symfony 的 view 大致上可以分為 Template 和 Layout，差別在 Layout 比 Template 大，或者說 Template 在 Layout 裡面。
<h1>List of Posts</h1>
<table>
<tr><th>Date</th><th>Title</th></tr>
<?php foreach ($posts as $post): ?>
<tr>
<td><?php echo $post['date'] ?></td>
<td><?php echo $post['title'] ?></td>
</tr>
<?php endforeach; ?>
</table>
MVC - View (Layout)
<?php
$title = 'List of Posts';
$content = include('mytemplate.php');
?>
<html>
<head>
<title><?php echo $title ?></title>
</head>
<body>
<?php echo $content ?>
</body>
</html>
實際在 Symfony 裡面每個檔案所在的地方不同，雖然一開始有點混亂，但是學習後會發現其實 Symfony 把檔案分配的很好，就類似設計很好的作業系統或者Mudlib之類的感覺吧。
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