PHP 5 provides a way for objects to be defined so it is possible to iterate
through a list of items, with, for example a
foreach
statement. By default,
all
visible
properties will be used
for the iteration.
例子 19-20. Simple Object Iteration
<?php
class
MyClass
{
public $var1
=
'value 1'
;
public $var2
=
'value 2'
;
public $var3
=
'value 3'
;
protected $protected
=
'protected var'
;
private $private
=
'private var'
;
function
iterateVisible
() {
echo
"MyClass::iterateVisible:\n"
;
foreach(
$this
as
$key
=>
$value
) {
print
"$key => $value
\n
"
;
}
}
}
$class
= new
MyClass
();
foreach(
$class
as
$key
=>
$value
) {
print
"$key => $value
\n
"
;
}
echo
"\n"
;
$class
->
iterateVisible
();
?>
|
上例将输出：
var1 => value 1
var2 => value 2
var3 => value 3
MyClass::iterateVisible:
var1 => value 1
var2 => value 2
var3 => value 3
protected => protected var
private => private var
|
|
As the output shows, the
foreach
iterated through all
visible
variables that can be
accessed. To take it a step further you can
implement
one
of PHP 5's internal
interface
named
Iterator
. This allows the object to decide what and how
the object will be iterated.
例子 19-21. Object Iteration implementing Iterator
<?php
class
MyIterator implements Iterator
{
private $var
= array();
public
function
__construct
(
$array
)
{
if (
is_array
(
$array
)) {
$this
->
var
=
$array
;
}
}
public
function
rewind
() {
echo
"rewinding\n"
;
reset
(
$this
->
var
);
}
public
function
current
() {
$var
=
current
(
$this
->
var
);
echo
"current: $var
\n
"
;
return
$var
;
}
public
function
key
() {
$var
=
key
(
$this
->
var
);
echo
"key: $var
\n
"
;
return
$var
;
}
public
function
next
() {
$var
=
next
(
$this
->
var
);
echo
"next: $var
\n
"
;
return
$var
;
}
public
function
valid
() {
$var
=
$this
->
current
() !==
false
;
echo
"valid:
{
$var
}\n
"
;
return
$var
;
}
}
$values
= array(
1
,
2
,
3
);
$it
= new
MyIterator
(
$values
);
foreach (
$it
as
$a
=>
$b
) {
print
"$a: $b
\n
"
;
}
?>
|
上例将输出：
rewinding
current: 1
valid: 1
current: 1
key: 0
0: 1
next: 2
current: 2
valid: 1
current: 2
key: 1
1: 2
next: 3
current: 3
valid: 1
current: 3
key: 2
2: 3
next:
current:
valid:
|
|
You can also define your class so that it doesn't have to define
all the
Iterator
functions by simply implementing
the PHP 5
IteratorAggregate
interface.
例子 19-22. Object Iteration implementing IteratorAggregate
<?php
class
MyCollection implements IteratorAggregate
{
private $items
= array();
private $count
=
0
;
// Required definition of interface IteratorAggregate
public
function
getIterator
() {
return new
MyIterator
(
$this
->
items
);
}
public
function
add
(
$value
) {
$this
->
items
[
$this
->
count
++] =
$value
;
}
}
$coll
= new
MyCollection
();
$coll
->
add
(
'value 1'
);
$coll
->
add
(
'value 2'
);
$coll
->
add
(
'value 3'
);
foreach (
$coll
as
$key
=>
$val
) {
echo
"key/value:
[
$key -> $val
]\n\n
"
;
}
?>
|
上例将输出：
rewinding
current: value 1
valid: 1
current: value 1
key: 0
key/value: [0 -> value 1]
next: value 2
current: value 2
valid: 1
current: value 2
key: 1
key/value: [1 -> value 2]
next: value 3
current: value 3
valid: 1
current: value 3
key: 2
key/value: [2 -> value 3]
next:
current:
valid:
|
|