树枝里没有这样的东西previous()。
你可以看看循环变量
在您的情况下，一种解决方法是构建自定义迭代器。
这是一个例子
/**
* Previous Next Iterator adds two methods to the ArrayIterator
*
* -> getPreviousElement() To get the previous element of the iterator
* -> getNextElement() To get the next element of the iterator
*
* These methods will not affect the internal pointer
*/
class PreviousNextIterator extends ArrayIterator
{
protected $indexKeys = array();
protected $keyIndexs = array();
protected $elements = array();
protected $dirty = true;
/**
* Constructor
*
* @param array $array Input Array
* @param integer $flags Flags
*/
public function __construct($array = array(), $flags = 0)
{
parent::__construct($array, $flags);
$this->load();
}
/**
* Helper class to self create from an ArrayIterator
*
* @param ArrayIterator $iterator ArrayIterator to fetch
* @return PreviousNextIterator New self instance
*/
public static function createFromIterator(ArrayIterator $iterator)
{
return new self($iterator->getArrayCopy());
}
/**
* Get the previous element of the iterator
*
* @return mixed Previous element
*/
public function getPreviousElement()
{
$index = $this->getIndexKey($this->key());
if (--$index < 0) {
return;
}
$key = $this->getKeyIndex($index);
return $this->elements[$key];
}
/**
* Get the next element of the iterator
*
* @return mixed Next element
*/
public function getNextElement()
{
$index = $this->getIndexKey($this->key());
if (++$index >= $this->count()) {
return;
}
$key = $this->getKeyIndex($index);
return $this->elements[$key];
}
/**
* Loads up the keys
*
* $this->elements
* Contains the copy of the iterator array
* Eg: [ 'a' => $fooInstance1, 'b' => $fooInstance2 ...]
*
* $this->keyIndexs
* Contains the keys indexed numerically
* Eg: [ 0 => 'a', 1 => 'b' ...]
*
* $this->indexKeys
* Contains the indexes of the keys
* Eg: [ 'a' => 0, 'b' => 1 ...]
*/
protected function load()
{
if (!$this->isDirty()) {
return;
}
$this->elements = $this->getArrayCopy();
$this->keyIndexs = array_keys($this->elements);
$this->indexKeys = array_flip($this->keyIndexs);
$this->dirty = false;
}
/**
* Checks whether the loader is dirty
*
* @return boolean
*/
protected function isDirty()
{
return $this->dirty;
}
/**
* Get the Index of a given key
*
* @param string $key Key name
* @return integer Key's index
*/
protected function getIndexKey($key)
{
$this->load();
return array_key_exists($key, $this->indexKeys)
? $this->indexKeys[$key]
: null;
}
/**
* Get the key of a given index
*
* @param integer $index Key's index
* @return string Key name
*/
protected function getKeyIndex($index)
{
$this->load();
return array_key_exists($index, $this->keyIndexs)
? $this->keyIndexs[$index]
: null;
}
/**
* Following methods overrides default methods which alters the iterator
* in order to create a "Dirty state" which will force the reload
*
* You just need to write them all so as to get a complete working class
*/
public function append($value)
{
$this->dirty = true;
return parent::append($value);
}
}
这个迭代器增加了两个方法getPreviousElement和getNextElement
Test Case
class Foo
{
protected $name;
public function __construct($name)
{
$this->name = $name;
}
}
$array = array(
'a' => new Foo('bar'),
'b' => 42,
'c' => new Foo('foobaz'),
'czz' => 'bleh',
);
$iterator = new PreviousNextIterator($array);
foreach ($iterator as $key => $value) {
echo '--- PREVIOUS ---', PHP_EOL;
var_dump($iterator->getPreviousElement());
echo '--- CURRENT ---', PHP_EOL;
var_dump($value);
echo '--- NEXT ---', PHP_EOL;
var_dump($iterator->getNextElement());
echo '----------------', PHP_EOL, PHP_EOL;
}
Outputs
--- PREVIOUS ---
NULL
--- CURRENT ---
object(Foo)#1 (1) {
["name":protected]=>
string(3) "bar"
}
--- NEXT ---
int(42)
----------------
--- PREVIOUS ---
object(Foo)#1 (1) {
["name":protected]=>
string(3) "bar"
}
--- CURRENT ---
int(42)
--- NEXT ---
object(Foo)#2 (1) {
["name":protected]=>
string(6) "foobaz"
}
----------------
--- PREVIOUS ---
int(42)
--- CURRENT ---
object(Foo)#2 (1) {
["name":protected]=>
string(6) "foobaz"
}
--- NEXT ---
string(4) "bleh"
----------------
--- PREVIOUS ---
object(Foo)#2 (1) {
["name":protected]=>
string(6) "foobaz"
}
--- CURRENT ---
string(4) "bleh"
--- NEXT ---
NULL
----------------
在您的过滤器示例中，您返回迭代器，只需替换
return $iterator;
经过
return PreviousNextIterator::createFromIterator($iterator);
然后像这样在 TWIG 中使用它
{% for i in items %}
{% if i == items.previousElement %}
<p>Yes</p>
{% endif %}
{% if i == items.nextElement %}
<p>Same Next</p>
{% endif %}
{% endfor %}