(三)从零编写PHP容器-解决类重复依赖创建

项目源码

功能实现

• 解决类重复依赖创建、解决相互依赖(A->B->A->B->...)、循环依赖(A->B->C->A->B->C->A->...)

代码实现 Container

    /**
     * 解决相互依赖及循环依赖判断
     * @param string $abstract
     * @param array $tmp
     * @return Closure|object
     * @throws ReflectionException
     */
    public function createObjectNoEach(string $abstract, array $tmp = [])
    {
        if ($tmpInstance = &$tmp[$abstract]) {
            return $tmpInstance;
        }
        $refClass = new ReflectionClass($abstract);
        if ($refClass->getName() === Closure::class) {
            return function (){};
        } elseif ($refClass->hasMethod('__construct')) {
            $_constructParams = array_map(function (ReflectionParameter $param) use ($abstract, $tmp) {
                if ($param->getClass()) {
                    if (array_key_exists($param->getClass()->getName(), $tmp)) {
                        throw new class('can not create a circular dependencies class object.') extends Exception implements ContainerExceptionInterface{ };
                    }
                    return $this->createObjectNoEach($param->getClass()->getName(), $tmp);
                } elseif ($param->isDefaultValueAvailable()) {
                    return $param->getDefaultValue();
                } elseif ($param->getType()) {
                    return [
                            'string' => '',
                            'int' => 0,
                            'array' => [],
                            'bool' => false,
                            'float' => 0.0,
                            'iterable' => [],
                            'callable' => function() {}
                        ][$param->getType()->getName()] ?? null;
                } else {
                    return null;
                }
            }, $refClass->getMethod('__construct')->getParameters());
        }
        return $tmpInstance = $refClass->newInstance(... ($_constructParams ?? []));
    }

实现思路

• 通过存储自动创建实例对象，在参数列表中出现相同的类时判断为循环并抛出异常

添加代码

1. 判断是否缓存有实例对象

if ($tmpInstance = &$tmp[$abstract]) {
    return $tmpInstance;
}

2. 判断自动创建的类是否被创建过，如果被创建过则认为是递归，抛出异常

if (array_key_exists($param->getClass()->getName(), $tmp)) {
    throw new class('can not create a circular dependencies class object.') extends Exception implements ContainerExceptionInterface{ };
}
return $this->createObjectNoEach($param->getClass()->getName(), $tmp);

3. 存储自动创建的类实例

return $tmpInstance = $refClass->newInstance(... ($_constructParams ?? []));

注

示例