检查是否存在自定义 Twig 函数，然后调用它 [英] Check if a custom Twig function exists and then call it

问题描述

我测试是否存在自定义 Twig 函数:

I test if a custom Twig function exists:

{% if methodExist('sg_datatables_render') %}
    {{ sg_datatables_render(datatable) }}
 {% else %}
    {{ datatable_render((datatable)) }}
{% endif %}

methodExist 是一个简单的Twig_Function:

 /**
 * @param $name
 * @return bool
 */
public function methodExist($name){

    if($this->container->get('twig')->getFunction($name)){
        return true;
    }else{
        return false;
    }
}

但我得到一个例外:

Unknown "sg_datatables_render" function. Did you mean "datatable_render"?
500 Internal Server Error - Twig_Error_Syntax

推荐答案

我试图复制这个，确实 {{ sg_datatables_render(datatable) }} 似乎总是导致 Twig_Error_Syntax sg_datatables_render 未注册为 Twig 函数时的异常.

I tried to replicate this, and indeed, {{ sg_datatables_render(datatable) }} seems to always cause a Twig_Error_Syntax exception when sg_datatables_render has not been registered as a Twig function.

然后我尝试了类似的方法.这很难看，但我想知道它是否有效.这个想法是创建一个不存在的函数来避免抛出异常:

I then tried something like this. It's ugly, but I wanted to know if it works. The idea is that a non-existing function will be created to avoid the exception being thrown:

$twig->addFunction(new Twig_Function('methodExist', function(Twig_Environment $twig, $name) {
    $hasFunction = $twig->getFunction($name) !== false;

    if (!$hasFunction) {
        // The callback function defaults to null so I have omitted it here
        return $twig->addFunction(new Twig_Function($name));
    }

    return $hasFunction;
}, ['needs_environment' => true]));

但它没有用.我还尝试在新函数中添加一个简单的回调函数，但没有成功.

But it didn't work. I also tried to add a simple callback function to the new function with no success.

我用过滤器尝试了同样的技巧，即:

I tried the same trick with filters, i.e.:

{% if filterExists('sg_datatables_render') %}
    {{ datatable|sg_datatables_render }}
 {% else %}
    {{ datatable|datatable_render }}
{% endif %}

它也没有用.

这样的事情确实有效(耶！):

Something like this does work (yay!):

$twig->addFunction(new Twig_Function('renderDatatable', function(Twig_Environment $twig, $datatable) {
    $sgFunction = $twig->getFunction('sg_datatables_render');

    if ($sgFunction !== false) {
        return $sgFunction->getCallable()($datatable);
    }

    return $twig->getFunction('datatable_render')->getCallable()($datatable);
}, ['needs_environment' => true]));

然后在 Twig 中:

And then in Twig:

{{ renderDatatable(datatable) }}

renderDatatable 函数专门用于渲染数据表，即它不像您的 methodExist 那样是通用/多用途函数，但它可以工作.您当然可以尝试自己创建一个更通用的实现.

The renderDatatable function is specific to rendering datatables, i.e. it's not a general/multipurpose function like your methodExist is, but it works. You can of course try to create a more general implementation yourself.

这是一种更通用的方法.为 methodExist 创建一个额外的 Twig 函数:

Here's a more general approach. Create an additional Twig function to accompany methodExist:

$twig->addFunction(new Twig_Function('fn', function(Twig_Environment $twig, $name, ...$args) {
     $fn = $twig->getFunction($name);

     if ($fn === false) {
         return null;
     }

     // You could add some kind of error handling here
     return $fn->getCallable()(...$args);
 }, ['needs_environment' => true]));

然后您可以将原始代码修改为:

Then you could modify your original code to this:

{% if methodExist('sg_datatables_render') %}
    {{ fn('sg_datatables_render', datatable) }}
 {% else %}
    {{ datatable_render((datatable)) }}
{% endif %}

甚至使用三元运算符:

{{ methodExist('sg_datatables_render') ? fn('sg_datatables_render', datatable) : datatable_render(datatable) }}

<小时>

PS

以下是我如何编写 methodExist 函数:

$twig->addFunction(new Twig_Function('methodExists', function(Twig_Environment $twig, $name) {
     return $twig->getFunction($name) !== false;
 }, ['needs_environment' => true]));

1. 我将 s 添加到函数名称的末尾，因为该函数会检查方法/函数是否存在s.
2. 我添加了 ['needs_environment' =>true] 所以我可以使用 $twig 而不是 $this->container->get('twig').(感谢 yceruto 提供的这个技巧.)
如果函数不存在，
3. getFunction 返回 false (查看文档)，所以我将函数体简化为单行返回语句.

1. I added s to the end of the function's name because the function checks whether a method/function exists.
2. I added ['needs_environment' => true] so I can use $twig instead of $this->container->get('twig'). (Kudos to yceruto for this tip.)
3. getFunction returns false if the function doesn't exist (see the docs), so I simplified the function body to a single-line return statement.

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