CakePHP 2.x:Model::afterFind() 上的 $primary 标志真的有用吗? [英] CakePHP 2.x: Is the $primary flag on Model::afterFind() actually useful?

问题描述

CakePHP 的 Model::afterFind() 回调看起来像:

CakePHP's Model::afterFind() callback looks like:

afterFind(array $results, boolean $primary = false)

根据文档:

$primary 参数指示当前模型是否是查询所基于的模型，或者该模型是否作为关联被查询.如果将模型作为关联进行查询，$results 的格式可能会有所不同.

The $primary parameter indicates whether or not the current model was the model that the query originated on or whether or not this model was queried as an association. If a model is queried as an association the format of $results can differ.

它们可以不同，但实验表明它们并不总是不同.据我所知，$primary 参数实际上并不是那么有用.如果将其设置为 false，您可能会也可能不会获得扁平化的数据结构，因此您可能会或可能不会收到可怕的无法将字符串偏移用作数组"错误消息.

They can differ, but experimentation shows that they don't always differ. As far as I can tell, the $primary parameter isn't actually all that useful. If it's set to false you may or may not get a flattened data structure, so you may or may not wind up with the dreaded "cannot use string offset as an array" error message.

虽然我还没有尝试过，但我基于文档的想法是完全忽略 $primary 标志，只检查数据:

Although I haven't tried it yet, my thought based on the documentation was to ignore the $primary flag altogether and just check the data:

public function afterFind($results, $primary = false) {
  if (array_key_exists(0, $results) {
    // operate on $results[0]['User']['fieldname']
  } else {
    // operate on $results['fieldname']
  }
  return $results;
}

这很黑，我不喜欢它，但它似乎比 $primary 更有用.

This is hackish and I don't like it, but it seems likely to be more useful than $primary.

明确地说，我的问题是:

Explicitly stated, my questions are:

1. $primary 标志的实际用途是什么?
2. 它对确定 $results 数组的结构没有有用，还是我错过了那里的某些东西，我是否正确?

1. What is the $primary flag actually useful for?
2. Am I correct that it is not useful for determining the structure of the $results array, or have I missed something there?

推荐答案

确实，$primary 参数似乎只在警告您 $results 格式的情况下有用代码> 是不可预测的.它在确定 $results 的格式时没有用.

Indeed the $primary parameter seems to only be useful in warning you of cases where the format of $results is unpredictable. It is not useful in determining the format of $results.

此处的更多信息:https://groups.google.com/forum/?fromgroups=#!topic/cake-php/Mqufi67UoFo

那里提供的解决方案是检查 !isset($results[$this->primaryKey]) 以查看 $results 的格式.这也有点小技巧，但可以说比检查键0"要好.

The solution offered there is to check !isset($results[$this->primaryKey]) to see what format $results is. This is also a bit of a hack, but arguably better than checking for a key '0'.

我最终想出的解决方案是做这样的事情:

The solution I ultimately came up with is to do something like this:

public function afterFind($results, $useless) {

    // check for the primaryKey field
    if(!isset($results[$this->primaryKey])) {
        // standard format, use the array directly
        $resultsArray =& $results;
    } else {
        // stupid format, create a dummy array
        $resultsArray = array(array());
        // and push a reference to the single value into our array
        $resultsArray[0][$this->alias] =& $results;
    }

    // iterate through $resultsArray
    foreach($resultsArray as &$result) {
        // operate on $result[$this->alias]['fieldname']
        // one piece of code for both cases. yay!
    }

    // return $results in whichever format it came in
    // as but with the values modified by reference
    return parent::afterFind($results, $useless);
}

这减少了代码重复，因为您不必两次编写字段更改逻辑(一次用于数组，一次用于非数组).

This reduces code duplication because you don't have to write your field alteration logic twice (once for an array and once for non-array).

您可以通过在方法结束时返回 $resultsArray 来完全避免引用内容，但我不确定如果 CakePHP(或其他一些父class) 期望 $results 以传入的方式传入.此外，这种方式没有复制 $results 数组的开销.

You may be able to avoid the references stuff altogether by just returning $resultsArray at the end of the method, but I wasn't sure what issues that might cause if CakePHP (or some other parent class) expects $results in the way it was passed in. Plus this way doesn't have the overhead of copying the $results array.

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