这章研究CI如何渲染View层。


Tips

输出控制

  • ob_系列。
  • 将数组的键值对转为从数组中将变量导入到当前的符号表。
int extract ( array &$var_array [, int $extract_type = EXTR_OVERWRITE [, string $prefix = NULL ]] )
  • 返回由 obj 指定的对象中定义的属性组成的关联数组。
array get_object_vars ( object $obj ) 
  • 参数:short_open_tag,短标签写法:<?=$xxx;?>

流程

  1. 确定视图文件是否存在,存在则获取文件路径。
  2. 打开输出控制
  3. 根据 嵌套级别决定进行输出还是保存到output的final_output内。(这里实现的很好,赞!)
  4. 最终,所有被缓存的输出将由 Output::_display()统一输出、处理。

源码

$this->load->view('myview', arrar('key' => 'value));

我们可以通过这种方式输出视图,它实际调用了Load.php 定义的全局函数 view()_ci_load() 跟进:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
/**
* View Loader
*
* Loads "view" files.
*
* @param string $view View name
* @param array $vars An associative array of data
* to be extracted for use in the view
* @param bool $return Whether to return the view output
* or leave it to the Output class
* @return object|string
*/
public function view($view, $vars = array(), $return = FALSE)
{
return $this->_ci_load(array('_ci_view' => $view, '_ci_vars' => $this->_ci_object_to_array($vars), '_ci_return' => $return));
}


/**
* Internal CI Data Loader
*
* Used to load views and files.
*
* Variables are prefixed with _ci_ to avoid symbol collision with
* variables made available to view files.
*
* @used-by CI_Loader::view()
* @used-by CI_Loader::file()
* @param array $_ci_data Data to load
* @return object
*/
protected function _ci_load($_ci_data)
{
// Set the default data variables
foreach (array('_ci_view', '_ci_vars', '_ci_path', '_ci_return') as $_ci_val)
{
$$_ci_val = isset($_ci_data[$_ci_val]) ? $_ci_data[$_ci_val] : FALSE;
}

$file_exists = FALSE;

// Set the path to the requested file
if (is_string($_ci_path) && $_ci_path !== '')
{
$_ci_x = explode('/', $_ci_path);
//将数组的内部指针指向最后一个单元以互殴文件名
$_ci_file = end($_ci_x);
}
else
{
$_ci_ext = pathinfo($_ci_view, PATHINFO_EXTENSION);
$_ci_file = ($_ci_ext === '') ? $_ci_view.'.php' : $_ci_view;

//尝试获取视图文件
foreach ($this->_ci_view_paths as $_ci_view_file => $cascade)
{
if (file_exists($_ci_view_file.$_ci_file))
{
$_ci_path = $_ci_view_file.$_ci_file;
$file_exists = TRUE;
break;
}

if ( ! $cascade)
{
break;
}
}
}

// 请求的文件不存在,报错。
if ( ! $file_exists && ! file_exists($_ci_path))
{
show_error('Unable to load the requested file: '.$_ci_file);
}


// 这让我们可以通过 $this->load->key 的方式调用 Controller 包含的变量。
// This allows anything loaded using $this->load (views, files, etc.)
// to become accessible from within the Controller and Model functions.
$_ci_CI =& get_instance();
foreach (get_object_vars($_ci_CI) as $_ci_key => $_ci_var)
{
if ( ! isset($this->$_ci_key))
{
$this->$_ci_key =& $_ci_CI->$_ci_key;
}
}

/*
* Extract and cache variables
*
* You can either set variables using the dedicated $this->load->vars()
* function or via the second parameter of this function. We'll merge
* the two types and cache them so that views that are embedded within
* other views can have access to these variables.
*/
if (is_array($_ci_vars))
{
$this->_ci_cached_vars = array_merge($this->_ci_cached_vars, $_ci_vars);
}

//从数组中将变量导入到当前的符号表
extract($this->_ci_cached_vars);

/*
* Buffer the output
*
* We buffer the output for two reasons:
* 1. Speed. You get a significant speed boost. 显著提高的速度
* 2. So that the final rendered template can be post-processed by
* the output class. Why do we need post processing? For one thing,
* in order to show the elapsed page load time. Unless we can
* intercept the content right before it's sent to the browser and
* then stop the timer it won't be accurate.
*/
// 打开输出缓冲,之后的输出将不会显示出来
ob_start();

// If the PHP installation does not support short tags we'll
// do a little string replacement, changing the short tags
// to standard PHP echo statements.
if ( ! is_php('5.4') && ! ini_get('short_open_tag') && config_item('rewrite_short_tags') === TRUE)
{
// 当服务器不支持 short_open_tag 时采用这种曲线救国的方法。
echo eval('?>'.preg_replace('/;*\s*\?>/', '; ?>', str_replace('<?=', '<?php echo ', file_get_contents($_ci_path))));
}
else
{
//包含
include($_ci_path); // include() vs include_once() allows for multiple views with the same name
}

log_message('info', 'File loaded: '.$_ci_path);

// Return the file data if requested
if ($_ci_return === TRUE)
{
$buffer = ob_get_contents();
@ob_end_clean();
return $buffer;
}

/*
* Flush the buffer... or buff the flusher?
* 处理视图嵌套视图: header.php body.php footer.php
*
* In order to permit views to be nested within
* other views, we need to flush the content back out(退回) whenever
* we are beyond(超过) the first level of output buffering so that
* it can be seen and included properly by the first included
* template and any subsequent ones. Oy!
*/
if (ob_get_level() > $this->_ci_ob_level + 1)
{
// 输出并关闭
ob_end_flush();
}
else
{
$_ci_CI->output->append_output(ob_get_contents());
@ob_end_clean();
}

return $this;
}