CodeIgniter 分页类 pagination 源代码分析

一、构造函数：构造函数的参数是初始化参数个数，先判断参数如果>0，则调用$this->initialize($params);初始化参数，然后判断是否给每一个链接添加CSS类

public function __construct($params = array())
{
if (count($params) > 0)
{
$this->initialize($params);
}

if ($this->anchor_class != '')
{
$this->anchor_class = 'class="'.$this->anchor_class.'" ';
}

log_message('debug', "Pagination Class Initialized");
}

二、initialize($params = array())：该函数首先判断初始化参数个数是否大于0，如果大于0，则利用foreach初始化参数

function initialize($params = array())
{
if (count($params) > 0)
{
foreach ($params as $key => $val)
{
if (isset($this->$key))
{
$this->$key = $val;
}
}
}
}

三、生成分页链接的函数：create_link()：

该函数

①：首先判断分页的数据总行数$this->total_rows和每页显示的数量$this->per_page如果有一个为0，则中止

if ($this->total_rows == 0 OR $this->per_page == 0)
{
return '';
}

②：计算总页数：

$num_pages = ceil($this->total_rows / $this->per_page);

③：如果只有一页，则不需要进行分页了

if ($num_pages == 1)
{
return '';
}

④：根据是否启用了use_page_numbers设置开始页码

if ($this->use_page_numbers)
{
$base_page = 1;
}
else
{
$base_page = 0;
}

⑤：确定当前页码：首先判断是否启用了查询字符串重写，如果是则判断页码是否等于开始页码，如果不等于开始页码，则用输入类的get方法获取$this->query_string_segment为当前页码。如果没有启用查询字符串重写，则使用uri方式

$CI =& get_instance();

if ($CI->config->item('enable_query_strings') === TRUE OR $this->page_query_string === TRUE)
{
if ($CI->input->get($this->query_string_segment) != $base_page)
{
$this->cur_page = $CI->input->get($this->query_string_segment);

// Prep the current page - no funny business!
$this->cur_page = (int) $this->cur_page;
}
}
else
{
if ($CI->uri->segment($this->uri_segment) != $base_page)
{
$this->cur_page = $CI->uri->segment($this->uri_segment);

// Prep the current page - no funny business!
$this->cur_page = (int) $this->cur_page;
}
}

⑥：设置当前页码为1，如果启用了use_page_numbers且$this->cur_page
== 0，则当前页码设置为开始页码

if ($this->use_page_numbers AND $this->cur_page == 0)
{
$this->cur_page = $base_page;
}

$this->num_links = (int)$this->num_links;

if ($this->num_links < 1)
{
show_error('Your number of links must be a positive number.');
}

if ( ! is_numeric($this->cur_page))
{
$this->cur_page = $base_page;
}

⑦：判断当前页码是否超出范围：

if ($this->use_page_numbers)
{
if ($this->cur_page > $num_pages)
{
$this->cur_page = $num_pages;
}
}
else
{
if ($this->cur_page > $this->total_rows)
{
$this->cur_page = ($num_pages - 1) * $this->per_page;
}
}

⑧：计算分页链接显示的开始页码和最后页码，例如，当前页码为4，$num_links设置为2，则显示23456页码

$start = (($this->cur_page - $this->num_links) > 0) ? $this->cur_page - ($this->num_links - 1) : 1;
$end   = (($this->cur_page + $this->num_links) < $num_pages) ? $this->cur_page + $this->num_links : $num_pages;

⑨：设置$base_url

if ($CI->config->item('enable_query_strings') === TRUE OR $this->page_query_string === TRUE)
{
$this->base_url = rtrim($this->base_url).'&'.$this->query_string_segment.'=';
}
else
{
$this->base_url = rtrim($this->base_url, '/') .'/';
}

⑩：初始化输出变量$output为空，且设置$first_link

$output = '';

// Render the "First" link
if  ($this->first_link !== FALSE AND $this->cur_page > ($this->num_links + 1))
{
$first_url = ($this->first_url == '') ? $this->base_url : $this->first_url;
$output .= $this->first_tag_open.'<a '.$this->anchor_class.'href="'.$first_url.'">'.$this->first_link.'</a>'.$this->first_tag_close;
}

⑪：设置$prev_link：需要判断是否启用了$use_page_numbers，还要判断$i是否等于0

if  ($this->prev_link !== FALSE AND $this->cur_page != 1)
{
if ($this->use_page_numbers)
{
$i = $uri_page_number - 1;
}
else
{
$i = $uri_page_number - $this->per_page;
}

if ($i == 0 && $this->first_url != '')
{
$output .= $this->prev_tag_open.'<a '.$this->anchor_class.'href="'.$this->first_url.'">'.$this->prev_link.'</a>'.$this->prev_tag_close;
}
else
{
$i = ($i == 0) ? '' : $this->prefix.$i.$this->suffix;
$output .= $this->prev_tag_open.'<a '.$this->anchor_class.'href="'.$this->base_url.$i.'">'.$this->prev_link.'</a>'.$this->prev_tag_close;
}

}

⑫：设置显示的数字页码：首先判
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断$this->display_pages是否不为假，则显示数字页码

if ($this->display_pages !== FALSE)
{
// Write the digit links
for ($loop = $start -1; $loop <= $end; $loop++)
{
if ($this->use_page_numbers)
{
$i = $loop;
}
else
{
$i = ($loop * $this->per_page) - $this->per_page;
}

if ($i >= $base_page)
{
if ($this->cur_page == $loop)
{
$output .= $this->cur_tag_open.$loop.$this->cur_tag_close; // Current page
}
else
{
$n = ($i == $base_page) ? '' : $i;

if ($n == '' && $this->first_url != '')
{
$output .= $this->num_tag_open.'<a '.$this->anchor_class.'href="'.$this->first_url.'">'.$loop.'</a>'.$this->num_tag_close;
}
else
{
$n = ($n == '') ? '' : $this->prefix.$n.$this->suffix;

$output .= $this->num_tag_open.'<a '.$this->anchor_class.'href="'.$this->base_url.$n.'">'.$loop.'</a>'.$this->num_tag_close;
}
}
}
}
}

⑬：设置$this->next_link和$this->last_link

// Render the "next" link
if ($this->next_link !== FALSE AND $this->cur_page < $num_pages)
{
if ($this->use_page_numbers)
{
$i = $this->cur_page + 1;
}
else
{
$i = ($this->cur_page * $this->per_page);
}

$output .= $this->next_tag_open.'<a '.$this->anchor_class.'href="'.$this->base_url.$this->prefix.$i.$this->suffix.'">'.$this->next_link.'</a>'.$this->next_tag_close;
}

// Render the "Last" link
if ($this->last_link !== FALSE AND ($this->cur_page + $this->num_links) < $num_pages)
{
if ($this->use_page_numbers)
{
$i = $num_pages;
}
else
{
$i = (($num_pages * $this->per_page) - $this->per_page);
}
$output .= $this->last_tag_open.'<a '.$this->anchor_class.'href="'.$this->base_url.$this->prefix.$i.$this->suffix.'">'.$this->last_link.'</a>'.$this->last_tag_close;
}

⑭：最后输出结果

$output = preg_replace("#([^:])//+#", "\\1/", $output);

// Add the wrapper HTML if exists
$output = $this->full_tag_open.$output.$this->full_tag_close;

return $output;