Yii2 Controller & Action

    public function runAction($route, $params = [])
    {
        $parts = $this->createController($route);
        if (is_array($parts)) {
            /* @var $controller Controller */
            list($controller, $actionID) = $parts;
            $oldController = Yii::$app->controller;
            Yii::$app->controller = $controller;
            //调用yii/base/controller中的runAction方法，执行相应的action
            $result = $controller->runAction($actionID, $params);
            Yii::$app->controller = $oldController;

            return $result;
        } else {
            $id = $this->getUniqueId();
            throw new InvalidRouteException('Unable to resolve the request "' . ($id === '' ? $route : $id . '/' . $route) . '".');
        }
    }

// route值可以为当前controller中的action id,
// 或module id/controller id/action id/这种格式
// 如果以“/”开头，将用application来处理，否则，用module来处理
public function run($route, $params = [])
{
        $pos = strpos($route, '/');
        if ($pos === false) {
            //如果没有“/”，则为action id，直接调用runAction来执行这个action。如：index
            return $this->runAction($route, $params);
        } elseif ($pos > 0) {
            //如果“/”在中间，由当前的module来处理这个route。如：product/index
            return $this->module->runAction($route, $params);
        } else {
            //如果以“/”开头，则用当前的application来处理这个route。如：/product/index;
            return Yii::$app->runAction(ltrim($route, '/'), $params);
        }
}

public function runAction($id, $params = [])
    {
        $action = $this->createAction($id);
        if ($action === null) {
            throw new InvalidRouteException('Unable to resolve the request: ' . $this->getUniqueId() . '/' . $id);
        }

        Yii::trace("Route to run: " . $action->getUniqueId(), __METHOD__);

        if (Yii::$app->requestedAction === null) {
            Yii::$app->requestedAction = $action;
        }

        $oldAction = $this->action;
        $this->action = $action;

        //用来保存当前控制器的所有父模块，顺序为由子模块到父模块
        $modules = [];
        $runAction = true;
        //获取当前控制器的所有的模块，并执行每个模块的beforeAction来检查当前的action是否可以执行
        //this->getModules()返回的数组顺序是从父模块到子模块，
        //所以beforeAction先从父模块检查，而afterAction正好相反.
        // call beforeAction on modules
        foreach ($this->getModules() as $module) {
            if ($module->beforeAction($action)) {
                array_unshift($modules, $module);
            } else {
                $runAction = false;
                break;
            }
        }

        $result = null;
        //如果所有的父模块都满足执行的条件
        if ($runAction && $this->beforeAction($action)) {
            // run the action
            //再判断当前控制器中是beforeAction，
            //最后由生成的action对象来执行runWithParams方法
            // 执行完后，再foreach执行afterAction方法
            $result = $action->runWithParams($params);

            $result = $this->afterAction($action, $result);

            // call afterAction on modules
            foreach ($modules as $module) {
                /* @var $module Module */
                $result = $module->afterAction($action, $result);
            }
        }

        $this->action = $oldAction;

        return $result;
    }

    public function createAction($id)
    {
        if ($id === '') {
            $id = $this->defaultAction;
        }
        $actionMap = $this->actions();
        //如果在actions方法中指定了Standalone Actions，则直接使用此动作
        if (isset($actionMap[$id])) {
            return Yii::createObject($actionMap[$id], [$id, $this]);
        } elseif (preg_match('/^[a-z0-9\\-_]+$/', $id) && strpos($id, '--') === false && trim($id, '-') === $id) {
            $methodName = 'action' . str_replace(' ', '', ucwords(implode(' ', explode('-', $id))));
            if (method_exists($this, $methodName)) {
                //如果当前控制器中存在这个actionXXX方法，
                //再通过反射生成方法，再次检查一遍，最后生成InlineAction
                $method = new \ReflectionMethod($this, $methodName);
                if ($method->isPublic() && $method->getName() === $methodName) {
                    return new InlineAction($id, $this, $methodName);
                }
            }
        }
        return null;
    }

//比如定义了动作 actionCrate($id,$name=null)
//那个这个函数的作用就是从params(一般为$_GET)中提取$id，$name,
//具体的实现在web\Controller.php和console\Controller.php中
public function bindActionParams($action, $params)
{
    return [];
}

//此方法是base/controller中bindActionParams方法的实现
public function bindActionParams($action, $params)
    {
        //先通过反射得到动作action的方法信息
        //判断是Inline Action还是Standalone Action
        if ($action instanceof InlineAction) {
            $method = new \ReflectionMethod($this, $action->actionMethod);
        } else {
            $method = new \ReflectionMethod($action, 'run');
        }

        $args = [];
        $missing = [];
        $actionParams = [];
        foreach ($method->getParameters() as $param) {
            //获取action中形参的名字
            $name = $param->getName();
            //判断形参和$_GET中的参数是否匹配
            if (array_key_exists($name, $params)) {
                //先判断形参的数据结构，如果是数组，再进一步判断实参
                if ($param->isArray()) {
                    //如果$_GET中的实参也为数组，直接返回值，否则把实参包装成数组
                    $args[] = $actionParams[$name] = is_array($params[$name]) ? $params[$name] : [$params[$name]];
                } elseif (!is_array($params[$name])) {
                    //如果$_GET中的实参不是数组，则直接返回值
                    $args[] = $actionParams[$name] = $params[$name];
                } else {
                    throw new BadRequestHttpException(Yii::t('yii', 'Invalid data received for parameter "{param}".', [
                        'param' => $name,
                    ]));
                }
                unset($params[$name]);
            } elseif ($param->isDefaultValueAvailable()) {
                //如果在$_GET中没有找到实参,则先判断形参是否有默认值
                $args[] = $actionParams[$name] = $param->getDefaultValue();
            } else {
                //action中定义的形参没有在$_GET中找到
                $missing[] = $name;
            }
        }

        //action中的参数有缺少，抛异常
        if (!empty($missing)) {
            throw new BadRequestHttpException(Yii::t('yii', 'Missing required parameters: {params}', [
                'params' => implode(', ', $missing),
            ]));
        }

        $this->actionParams = $actionParams;

        return $args;
    }