Biltz中的循环嵌套的错题分析

tpl文件：

<div>{{ BEGIN test }} <p> {{ $num }} &nbsp;&nbsp; {{ $titile }} <br>

          {{ BEGIN abc }} This is a TEST _ {{ $titile}}_{{$num}}<br> {{ END abc }}

          </p>{{ END test }}

  </div>

想实现的效果是：
 test中从1循环到4，作为4个

标签，每个

标签中都再循环一次abc，也是四行。

php的预定义数组：

$arr = array(
                         array('num'=>1,"titile"=>"The number 1"),
                         array('num'=>2,"titile"=>"The number 2"),
                         array('num'=>3,"titile"=>"The number 3"),
                         array('num'=>4,"titile"=>"The number 4"),
                 );
$arr2 = array(
                         array('num'=>11,"titile"=>"The number 11"),
                         array('num'=>12,"titile"=>"The number 12"),
                         array('num'=>13,"titile"=>"The number 13"),
                         array('num'=>14,"titile"=>"The number 14"),
                 ）；

php示例1

foreach($arr as $array){
                  $t->block("/test",$array);
｝
foreach($arr2 as $array){
                  $t->block("/test/abc",$array);
                  }

这个的结果是什么呢？是不是需要的结果呢？

1    The number 1

2    The number 2

3    The number 3

4    The number 4
This is a TEST _ The number 11_11
This is a TEST _ The number 12_12
This is a TEST _ The number 13_13
This is a TEST _ The number 14_14

在上例中，Blitz先对test进行了循环，所以先得到4行，然后又对/test/abc进行了循环，所以又得了四行，一共得了八行，而不是我们需要的结果。那么需要怎么做呢？
正确的写法：

foreach($arr as $array){
                  $t->block("/test",$array);
                  foreach($arr2 as $array){
                          $t->block("/test/abc",$array);
                  }

          }

结果如下：

1    The number 1
This is a TEST _ The number 11_11
This is a TEST _ The number 12_12
This is a TEST _ The number 13_13
This is a TEST _ The number 14_14

2    The number 2
This is a TEST _ The number 11_11
This is a TEST _ The number 12_12
This is a TEST _ The number 13_13
This is a TEST _ The number 14_14

3    The number 3
This is a TEST _ The number 11_11
This is a TEST _ The number 12_12
This is a TEST _ The number 13_13
This is a TEST _ The number 14_14

4    The number 4
This is a TEST _ The number 11_11
This is a TEST _ The number 12_12
This is a TEST _ The number 13_13
This is a TEST _ The number 14_14

思考：
在手册的6.2节中，也提到：

6.2. Slowdowns
Blitz performance receipes are the same as for any web-applications with CPU bottleneck. Following things in Blitz may slow down your application:

    lot of includes (all the data will seat in VFS cache almost immediately, but includes always add some kernel syscalls and need CPU to parse/initialize objects).
    lot of hash lookups to resolve path-variables $obj.smth.blabla, performance downgrades proportionally to the product number_of_variables*average_path_length
    lot of hash lookups back through the scope stack
    lot of block()/iterate() calls instead of preparing set data and just calling $View->display($data)
    lot of non-built-in Blitz methods in templates (user defined callbacks or PHP-functions)

但是要嵌套的循环，就必须使用block，所以还是建议尽量少使用嵌套。实际上对于模板来说，能输出变量已经能解决大多数的情况了，特别是要求性能（速度）的应用中，尽量少使用嵌套的循环。