|
| 1 | +Create your own framework... on top of the Symfony2 Components (part 5) |
| 2 | +======================================================================= |
| 3 | + |
| 4 | +The astute reader has noticed that our framework hardcodes the way specific |
| 5 | +"code" (the templates) is run. For simple pages like the ones we have created |
| 6 | +so far, that's not a problem, but if you want to add more logic, you would be |
| 7 | +forced to put the logic into the template itself, which is probably not a good |
| 8 | +idea, especially if you still have the separation of concerns principle in |
| 9 | +mind. |
| 10 | + |
| 11 | +Let's separate the template code from the logic by adding a new layer: the |
| 12 | +controller: *The controller mission is to generate a Response based on the |
| 13 | +information conveyed by the client Request.* |
| 14 | + |
| 15 | +Change the template rendering part of the framework to read as follows:: |
| 16 | + |
| 17 | + <?php |
| 18 | + |
| 19 | + // example.com/web/front.php |
| 20 | + |
| 21 | + // ... |
| 22 | + |
| 23 | + try { |
| 24 | + $request->attributes->add($matcher->match($request->getPathInfo())); |
| 25 | + $response = call_user_func('render_template', $request); |
| 26 | + } catch (Routing\Exception\ResourceNotFoundException $e) { |
| 27 | + $response = new Response('Not Found', 404); |
| 28 | + } catch (Exception $e) { |
| 29 | + $response = new Response('An error occurred', 500); |
| 30 | + } |
| 31 | + |
| 32 | +As the rendering is now done by an external function (``render_template()`` |
| 33 | +here), we need to pass to it the attributes extracted from the URL. We could |
| 34 | +have passed them as an additional argument to ``render_template()``, but |
| 35 | +instead, let's use another feature of the ``Request`` class called |
| 36 | +*attributes*: Request attributes lets you attach additional information about |
| 37 | +the Request that is not directly related to the HTTP Request data. |
| 38 | + |
| 39 | +You can now create the ``render_template()`` function, a generic controller |
| 40 | +that renders a template when there is no specific logic. To keep the same |
| 41 | +template as before, request attributes are extracted before the template is |
| 42 | +rendered:: |
| 43 | + |
| 44 | + function render_template($request) |
| 45 | + { |
| 46 | + extract($request->attributes->all(), EXTR_SKIP); |
| 47 | + ob_start(); |
| 48 | + include sprintf(__DIR__.'/../src/pages/%s.php', $_route); |
| 49 | + |
| 50 | + return new Response(ob_get_clean()); |
| 51 | + } |
| 52 | + |
| 53 | +As ``render_template`` is used as an argument to the PHP ``call_user_func()`` |
| 54 | +function, we can replace it with any valid PHP `callbacks`_. This allows us to |
| 55 | +use a function, an anonymous function, or a method of a class as a |
| 56 | +controller... your choice. |
| 57 | + |
| 58 | +As a convention, for each route, the associated controller is configured via |
| 59 | +the ``_controller`` route attribute:: |
| 60 | + |
| 61 | + $routes->add('hello', new Routing\Route('/hello/{name}', array( |
| 62 | + 'name' => 'World', |
| 63 | + '_controller' => 'render_template', |
| 64 | + ))); |
| 65 | + |
| 66 | + try { |
| 67 | + $request->attributes->add($matcher->match($request->getPathInfo())); |
| 68 | + $response = call_user_func($request->attributes->get('_controller'), $request); |
| 69 | + } catch (Routing\Exception\ResourceNotFoundException $e) { |
| 70 | + $response = new Response('Not Found', 404); |
| 71 | + } catch (Exception $e) { |
| 72 | + $response = new Response('An error occurred', 500); |
| 73 | + } |
| 74 | + |
| 75 | +A route can now be associated with any controller and of course, within a |
| 76 | +controller, you can still use the ``render_template()`` to render a template:: |
| 77 | + |
| 78 | + $routes->add('hello', new Routing\Route('/hello/{name}', array( |
| 79 | + 'name' => 'World', |
| 80 | + '_controller' => function ($request) { |
| 81 | + return render_template($request); |
| 82 | + } |
| 83 | + ))); |
| 84 | + |
| 85 | +This is rather flexible as you can change the Response object afterwards and |
| 86 | +you can even pass additional arguments to the template:: |
| 87 | + |
| 88 | + $routes->add('hello', new Routing\Route('/hello/{name}', array( |
| 89 | + 'name' => 'World', |
| 90 | + '_controller' => function ($request) { |
| 91 | + // $foo will be available in the template |
| 92 | + $request->attributes->set('foo', 'bar'); |
| 93 | + |
| 94 | + $response = render_template($request); |
| 95 | + |
| 96 | + // change some header |
| 97 | + $response->headers->set('Content-Type', 'text/plain'); |
| 98 | + |
| 99 | + return $response; |
| 100 | + } |
| 101 | + ))); |
| 102 | + |
| 103 | +Here is the updated and improved version of our framework:: |
| 104 | + |
| 105 | + <?php |
| 106 | + |
| 107 | + // example.com/web/front.php |
| 108 | + |
| 109 | + require_once __DIR__.'/../vendor/.composer/autoload.php'; |
| 110 | + |
| 111 | + use Symfony\Component\HttpFoundation\Request; |
| 112 | + use Symfony\Component\HttpFoundation\Response; |
| 113 | + use Symfony\Component\Routing; |
| 114 | + |
| 115 | + function render_template($request) |
| 116 | + { |
| 117 | + extract($request->attributes->all(), EXTR_SKIP); |
| 118 | + ob_start(); |
| 119 | + include sprintf(__DIR__.'/../src/pages/%s.php', $_route); |
| 120 | + |
| 121 | + return new Response(ob_get_clean()); |
| 122 | + } |
| 123 | + |
| 124 | + $request = Request::createFromGlobals(); |
| 125 | + $routes = include __DIR__.'/../src/app.php'; |
| 126 | + |
| 127 | + $context = new Routing\RequestContext(); |
| 128 | + $context->fromRequest($request); |
| 129 | + $matcher = new Routing\Matcher\UrlMatcher($routes, $context); |
| 130 | + |
| 131 | + try { |
| 132 | + $request->attributes->add($matcher->match($request->getPathInfo())); |
| 133 | + $response = call_user_func($request->attributes->get('_controller'), $request); |
| 134 | + } catch (Routing\Exception\ResourceNotFoundException $e) { |
| 135 | + $response = new Response('Not Found', 404); |
| 136 | + } catch (Exception $e) { |
| 137 | + $response = new Response('An error occurred', 500); |
| 138 | + } |
| 139 | + |
| 140 | + $response->send(); |
| 141 | + |
| 142 | +To celebrate the birth of our new framework, let's create a brand new |
| 143 | +application that needs some simple logic. Our application has one page that |
| 144 | +says whether a given year is a leap year or not. When calling |
| 145 | +``/is_leap_year``, you get the answer for the current year, but the you can |
| 146 | +also specify a year like in ``/is_leap_year/2009``. Being generic, the |
| 147 | +framework does not need to be modified in any way, just create a new |
| 148 | +``app.php`` file:: |
| 149 | + |
| 150 | + <?php |
| 151 | + |
| 152 | + // example.com/src/app.php |
| 153 | + |
| 154 | + use Symfony\Component\Routing; |
| 155 | + use Symfony\Component\HttpFoundation\Response; |
| 156 | + |
| 157 | + function is_leap_year($year = null) { |
| 158 | + if (null === $year) { |
| 159 | + $year = date('Y'); |
| 160 | + } |
| 161 | + |
| 162 | + return 0 == $year % 400 || (0 == $year % 4 && 0 != $year % 100); |
| 163 | + } |
| 164 | + |
| 165 | + $routes = new Routing\RouteCollection(); |
| 166 | + $routes->add('leap_year', new Routing\Route('/is_leap_year/{year}', array( |
| 167 | + 'year' => null, |
| 168 | + '_controller' => function ($request) { |
| 169 | + if (is_leap_year($request->attributes->get('year'))) { |
| 170 | + return new Response('Yep, this is a leap year!'); |
| 171 | + } |
| 172 | + |
| 173 | + return new Response('Nope, this is not a leap year.'); |
| 174 | + } |
| 175 | + ))); |
| 176 | + |
| 177 | + return $routes; |
| 178 | + |
| 179 | +The ``is_leap_year()`` function returns ``true`` when the given year is a leap |
| 180 | +year, ``false`` otherwise. If the year is null, the current year is tested. |
| 181 | +The controller is simple: it gets the year from the request attributes, pass |
| 182 | +it to the `is_leap_year()`` function, and according to the return value it |
| 183 | +creates a new Response object. |
| 184 | + |
| 185 | +As always, you can decide to stop here and use the framework as is; it's |
| 186 | +probably all you need to create simple websites like those fancy one-page |
| 187 | +`websites`_ and hopefully a few others. |
| 188 | + |
| 189 | +.. _`callbacks`:http://php.net/callback#language.types.callback |
| 190 | +.. _`websites`:http://kottke.org/08/02/single-serving-sites |