Home arrow PHP arrow Page 4 - Implementing the Iterator SPL Interface

The full source code of the MySQLi_ResultWrapper class - PHP

In this second part of a series, I make the MySQLi_ResultWrapper class a full implementer of the Iterator SPL interface. Implementing the rest of the methods declared by the interface is a straightforward process that allows us to traverse MySQL result sets by using a plain “foreach” construct.

TABLE OF CONTENTS:
  1. Implementing the Iterator SPL Interface
  2. Review: partially implementing partially the Iterator SPL interface
  3. Implementing the remaining methods of the Iterator interface
  4. The full source code of the MySQLi_ResultWrapper class
By: Alejandro Gervasio
Rating: starstarstarstarstar / 2
March 18, 2010

print this article
SEARCH DEV SHED

TOOLS YOU CAN USE

advertisement

If you’re anything like me, then you want to see the finished version of the previous “MySQLi_ResultWrapper” class, now that it fully implements the Iterator SPL interface. In that case, look at the following example, which shows the class’s source code:

  class MySQLi_ResultWrapper extends MySQLi_Result implements Iterator

{

    private $_pointer = 0;

   

   // fetch row as an object

    public function fetchObject()

    {

        if (!$row = $this->fetch_object())

        {

            return NULL;

        }

        return $row;

    }

   

    // fetch row as an associative array

    public function fetchAssocArray()

    {

        if (!$row = $this->fetch_assoc())

        {

            return NULL;

        }

        return $row;

    }

   

    // fetch row as an enumerated array

    public function fetchNumArray()

    {

        if (!$row = $this->fetch_row())

        {

            return NULL;

        }

        return $row;

    }

   

    // fetch all rows

    public function fetchAll($type = MYSQLI_ASSOC)

    {

        if ($type !== MYSQLI_ASSOC AND $type !== MYSQLI_NUM AND $type !== MYSQLI_BOTH)

        {

            $type = MYSQLI_ASSOC;

        }

        if (!$rows = $this->fetch_all($type))

        {

            return NULL;

        }

        return $rows;  

    }

   

    // get definition information on fields

      public function fetchFieldsInfo()

    {

        if (!$fieldsInfo = $this->fetch_fields())

        {

            throw new Exception('No information available for table fields.');

        }

        return $fieldsInfo;

    }

   

    // get definition information on next field

    public function fetchFieldInfo()

    {

        if (!$fieldInfo = $this->fetch_field())

        {

            throw new Exception('No information available for current table field.');   

        }

        return $fieldInfo;

    }

   

    // move pointer in result set to specified offset

    public function movePointer($offset)

    {

        $offset = abs((int)$offset);

        $limit = $this->num_rows - 1;

        if ($limit <= 0 OR $offset > $limit)

        {

            return NULL;

        }

        unset($limit);

        return $this->data_seek($offset);

      }

       

    // reset result set pointer (implementation required by 'rewind()' method in Iterator interface)

    public function rewind()

    {

        $this->_pointer = 0;

        $this->movePointer($this->_pointer);

        return $this; 

    }

   

    // get current row set in result set (implementation required by 'current()' method in Iterator interface)

    public function current()

    {

        if (!$this->valid())

        {

            throw new Exception('Unable to retrieve current row.');

        }

        $this->movePointer($this->_pointer);

        return $this->fetchObject();

    }

   

    // get current result set pointer (implementation required by 'key()' method in Iterator interface)

    public function key()

    {

        return $this->_pointer;

    }

   

    // move forward result set pointer (implementation required by 'next()' method in Iterator interface)

    public function next()

    {

        ++$this->_pointer;

        $this->movePointer($this->_pointer);

        return $this;

    }

   

    // determine if result set pointer is valid or not (implementation required by 'valid()' method in Iterator interface)

    public function valid()

    {

        return $this->_pointer < $this->num_rows;

    }

}

Mission accomplished. Now the “MySQLi_ResultWrapper” class suits the requirements imposed by Iterator, as it implements all of the interface’s methods. Even though at this point the class is capable of iterating over a retrieved data set by using a “foreach” loop, it does not have a method that allows it to count the number of rows in the set.

Fortunately, this issue can be easily addressed by making the class an implementer of the Countable SPL interface. However, that will be addressed in the next tutorial in this series. 

Final thoughts

In this second part of the series, I made the previous "MySQLi_ResultWrapper” class a full implementer of the Iterator SPL interface. As you saw for yourself, implementing the rest of the methods declared by the interface was indeed a straightforward process, and allowed us to traverse MySQL result sets by using a plain “foreach” construct.

In the upcoming tutorial, I’m going to give the aforementioned class the ability to count rows in data sets by implementing the “count()” method declared by the Countable SPL interface.

Don’t miss the forthcoming article!



 
 
>>> More PHP Articles          >>> More By Alejandro Gervasio
 

blog comments powered by Disqus
escort Bursa Bursa escort Antalya eskort
   

PHP ARTICLES

- Hackers Compromise PHP Sites to Launch Attac...
- Red Hat, Zend Form OpenShift PaaS Alliance
- PHP IDE News
- BCD, Zend Extend PHP Partnership
- PHP FAQ Highlight
- PHP Creator Didn't Set Out to Create a Langu...
- PHP Trends Revealed in Zend Study
- PHP: Best Methods for Running Scheduled Jobs
- PHP Array Functions: array_change_key_case
- PHP array_combine Function
- PHP array_chunk Function
- PHP Closures as View Helpers: Lazy-Loading F...
- Using PHP Closures as View Helpers
- PHP File and Operating System Program Execut...
- PHP: Effects of Wrapping Code in Class Const...

Developer Shed Affiliates

 


Dev Shed Tutorial Topics: