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Review: the delete() method - PHP

Welcome to the eighth installment of a series on method chaining in PHP 5. With numerous code samples, this series shows you how to define chainable methods within your own PHP classes. Best of all, it teaches you how to implement this powerful programming method in a real-world case: developing an abstract model for the CodeIgniter framework.

TABLE OF CONTENTS:
  1. Expanding a Custom CodeIgniter Library with Method Chaining
  2. Review: the delete() method
  3. The chainable select() and select_max() methods
  4. The AbstractModel class's full source code
By: Alejandro Gervasio
Rating: starstarstarstarstar / 1
November 16, 2009

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Prior to coding these new methods, I'm going to reintroduce the signature of the “AbstractModel” class as it was in the previous tutorial. Here is the full source code for the class. Please look it over: 

The MIT License

 

Copyright (c) 2008 Simon Stenhouse

 

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

 

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

 

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 

 

class AbstractModel

{

protected $table = '';

protected $fields = array();

protected $validation = array();

protected $error_prefix = '<p>';

protected static $instance = NULL;

protected $ci = NULL;

protected $db = NULL;

 

// Factory method that creates a singleton model object

public static function factory($model)

{

if (self::$instance == NULL)

{

$model = ucfirst($model);

self::$instance = new $model;

}

return self::$instance;

}

 

// Constructor

public function __construct()

{

$this->ci = & get_instance();

$this->db = $this->ci->db;

$table = strtolower(get_class($this)) . 's';

if ($this->db->table_exists($table))

{

$this->table = $table;

$this->fields = $this->db->field_names($this->table);

}

else

{

return;

}

}

 

// Sets a new property for the model

function __set($property, $value)

{

if(in_array($property, array_merge($this->fields, array('error', 'result')), TRUE))

{

$this->$property = $value;

}

}

 

// Gets the value of an existing property of the model

function __get($property)

{

if(isset($this->$property))

{

return $this->$property;

}

return NULL;

}

 

// Fetches rows from specified table

public function fetch($limit = NULL, $offset = NULL)

{

$data = array();

foreach ($this->fields as $field)

{

if (isset($this->$field) AND $this->$field != '')

{

$data[$field] = $this->$field;

}

}

$query = !empty($data) ? $this->db->get_where($this->table, $data, $limit, $offset) : $this->db->get($this->table, $limit, $offset);

if ($query->num_rows() > 0)

{

$this->result = $query->result();

return $this;

}

$this->error = 'No rows were returned.';

return FALSE;

}

 

// Inserts a new row into the specified database table

public function save()

{

$data = array();

foreach ($this->fields as $field)

{

if (isset($this->$field))

{

$data[$field] = $this->$field;

 

}

}

// if there is any data available go ahead and save/update row

if( !empty($data))

{

// validate input data

if ($this->validate($data) === FALSE)

{

$this->error = $this->get_error_string();

return FALSE;

}

// if id property has been set in the controller update existing row

if ( !empty($this->id))

{

// Update existing record

$this->db->where('id', $this->id);

$this->db->update($this->table, $data);

}

else

{

// otherwise insert new row

$this->db->insert($this->table, $data);

$this->id = $this->db->insert_id();

}

return TRUE;

}

$this->error = 'No valid data was provided to save row.';

return FALSE;

}

}

Hopefully, after having reexamined the definition of the previous “AbstractModel” class, you’ll recall how its current methods were implemented. In this case, it’s clear to see how the method chaining approach has been applied to build the “factory()” and “fetch()” methods, which speaks for itself about the functionality of this technique.

So far, so good. Now, it’s time to continue expanding the functionality of the custom model for CodeIgniter, since at this time it’s only capable of fetching and inserting/updating database rows. Therefore, I’m going to add another method, which will be tasked with deleting records.

The implementation of this brand new method, not surprisingly called “delete(),” is shown below. Look at it, please:

// Deletes a row

public function delete()

{

if (isset($this->id))

{

$this->db->where('id', $this->id);

$this->db->delete($this->table);

return TRUE;

}

$this->error = 'Error deleting row.';

return FALSE;

}

Short and effective, right? As you can see, the above “delete()” method is tasked with removing a specified row or rows from the corresponding database table. If this operation fails for whatever reason, the method will store an error message on the “error” property and returns a value of FALSE. Otherwise, it’ll return TRUE.

Having now provided the custom model for CodeIgniter with the ability to delete database records, it’s time to extend its current functionality even more. In the section to come I’m going to add to the model a couple of chainable methods, which as you’ll see in short, will be capable of building the SELECT and SELECT MAX part of a SQL query.

Thus, to learn the full details on how these new methods will be created, click on the link below and keep reading.



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

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