时间：2021-07-01 10:21:17 帮助过：1人阅读
//看个例子
class My{
private $_data = [
'a' => '燕睿涛',
'b' => 'yanruitao',
'c' => 'LULU',
];
public function getIterator()
{
return new ArrayIterator($this->_data);
}
}
$obj = new My;
foreach ($obj as $key => $value) {
echo "$key => $value\n";
}
//输出结果为空
class My implements IteratorAggregate {
private $_data = [
'a' => '燕睿涛',
'b' => 'yanruitao',
'c' => 'LULU',
];
public function getIterator()
{
return new ArrayIterator($this->_data);
}
}
$obj = new My;
foreach ($obj as $key => $value) {
echo "$key => $value\n";
}
//结果：
a => 燕睿涛
b => yanruitao
c => LULU
Countable
Countable {
abstract public int count(void)
}
这个接口用于统计对象的数量，具体怎么理解呢，当我们对一个对象调用count的时候，如果函数没有继承Countable将一直返回1，如果继承了Countable会返回所实现的count方法所返回的数字，看看下面的例子：
class CountMe
{
protected $_myCount = 3;
public function count()
{
return $this->_myCount;
}
}
$countable = new CountMe();
echo count($countable);
//返回1
class CountMe implements Countable
{
protected $_myCount = 3;
public function count()
{
return $this->_myCount;
}
}
$countable = new CountMe();
echo count($countable);
//返回3
ArrayAccess
ArrayAccess {
abstract public boolean offsetExists(mixed $offset)
abstract public mixed offsetGet(mixed $offset)
public void offsetSet(mixed $offset, mixed $value)
public void offsetUnset(mixed $offset)
}
这个接口的作用是让我们可以像访问数组一样访问对象，这个怎么说好呢，我猜其实就是php在词法分析的时候如果碰到了数组的方式使用对象，就回去对象中查找是否有实现ArrayAccess如果有的话，进行对应的操作（set、unset、isset、get），这样我们就可以在类里面放置一个array，让类实现数组方式的基本操作，下面看个例子：
class myObj
{
}
$obj = new myObj;
$obj['name'];
//Fatal error: Cannot use object of type myObj as array in
class myObj implements ArrayAccess
{
public function offsetSet($offset, $value)
{
echo "offsetSet : {$offset} => {$value}\n";
}
public function offsetExists($offset)
{
echo "offsetExists : {$offset}\n";
}
public function offsetUnset($offset)
{
echo "offsetUnset : {$offset}\n";
}
public function offsetGet($offset)
{
echo "offsetGet : {$offset}\n";
}
}
$obj = new myObj;
$obj[1] = '燕睿涛';
isset($obj['name']);
unset($obj['name']);
$obj['yrt'];
//输出结果：
offsetSet : 1 => 燕睿涛
offsetExists : name
offsetUnset : name
offsetGet : yrt
class myObj implements ArrayAccess
{
private $_data = [];
public function offsetSet($offset, $value)
{
$this->_data[$offset] = $value;
}
public function offsetExists($offset)
{
return isset($this->_data[$offset]);
}
public function offsetUnset($offset)
{
unset($this->_data[$offset]);
}
public function offsetGet($offset)
{
return $this->_data[$offset];
}
}
$obj = new myObj;
$obj['yrt'] = '燕睿涛';
var_dump($obj['yrt']);
var_dump(isset($obj['yrt']));
unset($obj['yrt']);
var_dump(isset($obj['yrt']));
var_dump($obj['yrt']);
//输出：
string(9) "燕睿涛"
bool(true)
bool(false)
Notice: Undefined index: yrt //最后一个会报出Notice
上面的对象只能是基本的数组操作，连遍历都不行，结合之前的IteratorAggregate可以进行foreach:
class myObj implements ArrayAccess, IteratorAggregate
{
private $_data = [];
public function getIterator()
{
return new ArrayIterator($this->_data);
}
......
}
$obj = new myObj;
$obj['yrt'] = '燕睿涛';
$obj[1] = '燕睿涛';
$obj['name'] = '燕睿涛';
$obj['age'] = 23;
foreach ($obj as $key => $value) {
echo "{$key} => {$value}\n";
}
//输出：
yrt => 燕睿涛
1 => 燕睿涛
name => 燕睿涛
age => 23
Iterator
Iterator extends Traversable {
abstract public mixed current(void)
abstract public scalar key(void)
abstract public void next(void)
abstract public void rewind(void)
abstract public boolean valid(void)
}
可在内部迭代自己的外部迭代器或类的接口，这是官方文档给出的解释，看着还是不好理解，其实我感觉这个接口实现的功能和trratorAggregate（文档：创建外部迭代器接口，接口直接返回一个迭代器）类似，不过这个在类的定义里面自己实现了，看个例子：
class myObj implements Iterator{
private $_data = [];
public function __construct(Array $arr)
{
$this->_data = $arr;
}
public function current()
{
return current($this->_data);
}
public function key()
{
return key($this->_data);
}
public function next()
{
next($this->_data);
}
public function rewind()
{
reset($this->_data);
}
public function valid()
{
return $this->key() !== NULL;
}
}
$t = [
'yrt' => '燕睿涛',
'name' => '燕睿涛',
false,
'燕睿涛'
];
$obj = new myObj($t);
foreach ($obj as $key => $value) {
echo "{$key} => ".var_export($value, true)."\n";
}
//输出：
yrt => '燕睿涛'
name => '燕睿涛'
0 => false
1 => '燕睿涛'
上面这个参考了鸟哥的一篇文章关于一笔试题(Iterator模式)，不过鸟哥的那个判断valid有点瑕疵，当碰到值北来就是false的时候就会截断
http://www.bkjia.com/PHPjc/1039604.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/1039604.htmlTechArticlePHP预定义接口 引言 在PHP中有好几个预定义的接口，还挺有用的 IteratorAggregate（聚合式aggregate迭代器Iterator） IteratorAggregate extends Traversable...