Joomla JDatabase: selectRowNumber 奇怪使用 class 属性或方法

Question

in Joomla 3.9.16 there is a strage use of a class attribute that is also used as a method!

In libraries/joomla/database/query.php you can find:

protected $selectRowNumber = null;

but also

public function selectRowNumber($orderBy, $orderColumnAlias)
{
  $this->validateRowNumber($orderBy, $orderColumnAlias);
  $this->select("ROW_NUMBER() OVER (ORDER BY $orderBy) AS $orderColumnAlias");

  return $this;
}

You can undestand why reading this method of the same class:

protected function validateRowNumber($orderBy, $orderColumnAlias)
{
  if ($this->selectRowNumber)
  {
    throw new RuntimeException("Method 'selectRowNumber' can be called only once per instance.");
  }

  $this->type = 'select';

  $this->selectRowNumber = array(
    'orderBy' => $orderBy,
    'orderColumnAlias' => $orderColumnAlias,
  );
}

When you call $this->selectRowNumber() as a method for the first time, it calls $this->validateRowNumber() in which $this->selectRowNumber() becomes an array! If you call again $this->selectRowNumber() it throws an exception because you can call it only once and is no more a method.

I wonder if this is a good programming practice, I think definitely NOT because is not easy to understand and mantain. Maybe you can achive the same result in another way much more clear and linear. What I ask is: am I right or this is a common practice?

Thanks

Answer 1

Are you saying that you can reproduce this fault? I am going to assume that you are misreading the script.

It looks to me that the selectRowNumber() method is called the first time and then inside validateRowNumber() , the class variable/property $this->selectRowNumber is checked for truthiness.

Since it is null (falsey) the first time, no exception is thrown.

The class variable/property (not the method) is updated with

$this->selectRowNumber = array(
    'orderBy' => $orderBy,
    'orderColumnAlias' => $orderColumnAlias,
  );

Then back inside selectRowNumber() , the ROW_NUMBER() OVER (ORDER BY $orderBy) AS $orderColumnAlias string is applied to $this->select() .

Because ROW_NUMBER() OVER (ORDER BY $orderBy) AS $orderColumnAlias must not be applied twice to a given query, the safeguard / thrown Exception checks for a truthy class variable/property -- which of course it is because it has been modified from null to a non-empty associative array.

Is it confusing to have properties and methods sharing the same name? Sure. The only distinction between the two is the trailing () .

Is this acceptable coding practice? Well, in terms of readability it's not ideal. But once a project standardizes its naming convention, sometimes these kinds of converging names happen. The bigger the code base, the more likely this is to occur. I think consistency is more important than readability in this isolated situation.