php定义枚举,PHP中Enum(枚举)用法实例详解
本文實例講述了PHP中Enum(枚舉)用法。分享給大家供大家參考，具體如下：
PHP其實有Enum類庫的，需要安裝perl擴展，所以不是php的標準擴展，因此代碼的實現需要運行的php環境支持。
(1)擴展類庫SplEnum類。該類的摘要如下：
SplEnum extends SplType {
/* Constants */
const NULL __default = null ;
/* 方法 */
public array getConstList ([ bool $include_default = false ] )
/* 繼承的方法 */
SplType::__construct ([ mixed $initial_value [, bool $strict ]] )
}
使用示例：
class Month extends SplEnum {
const __default = self::January;
const January = 1;
const February = 2;
const March = 3;
const April = 4;
const May = 5;
const June = 6;
const July = 7;
const August = 8;
const September = 9;
const October = 10;
const November = 11;
const December = 12;
}
echo new Month(Month::June) . PHP_EOL;
try {
new Month(13);
} catch (UnexpectedValueException $uve) {
echo $uve->getMessage() . PHP_EOL;
}
?>
輸出結果：
6
Value not a const in enum Month
(2)自定義的Enum類庫
/**
* Abstract class that enables creation of PHP enums. All you
* have to do is extend this class and define some constants.
* Enum is an object with value from on of those constants
* (or from on of superclass if any). There is also
* __default constat that enables you creation of object
* without passing enum value.
*
* @author Marijan ?uflaj
* @link http://php4every1.com
*/
abstract class Enum {
/**
* Constant with default value for creating enum object
*/
const __default = null;
private $value;
private $strict;
private static $constants = array();
/**
* Returns list of all defined constants in enum class.
* Constants value are enum values.
*
* @param bool $includeDefault If true, default value is included into return
* @return array Array with constant values
*/
public function getConstList($includeDefault = false) {
$class = get_class($this);
if (!array_key_exists($class, self::$constants)) {
self::populateConstants();
}
return $includeDefault ? array_merge(self::$constants[__CLASS_], array(
"__default" => self::__default
)) : self::$constants[__CLASS_];
}
/**
* Creates new enum object. If child class overrides __construct(),
* it is required to call parent::__construct() in order for this
* class to work as expected.
*
* @param mixed $initialValue Any value that is exists in defined constants
* @param bool $strict If set to true, type and value must be equal
* @throws UnexpectedValueException If value is not valid enum value
*/
public function __construct($initialValue = null, $strict = true) {
$class = get_class($this);
if (!array_key_exists($class, self::$constants)) {
self::populateConstants();
}
if ($initialValue === null) {
$initialValue = self::$constants[$class]["__default"];
}
$temp = self::$constants[$class];
if (!in_array($initialValue, $temp, $strict)) {
throw new UnexpectedValueException("Value is not in enum " . $class);
}
$this->value = $initialValue;
$this->strict = $strict;
}
private function populateConstants() {
$class = get_class($this);
$r = new ReflectionClass($class);
$constants = $r->getConstants();
self::$constants = array(
$class => $constants
);
}
/**
* Returns string representation of an enum. Defaults to
* value casted to string.
*
* @return string String representation of this enum's value
*/
public function __toString() {
return (string) $this->value;
}
/**
* Checks if two enums are equal. Only value is checked, not class type also.
* If enum was created with $strict = true, then strict comparison applies
* here also.
*
* @return bool True if enums are equal
*/
public function equals($object) {
if (!($object instanceof Enum)) {
return false;
}
return $this->strict ? ($this->value === $object->value)
: ($this->value == $object->value);
}
}
使用示例如下：
class MyEnum extends Enum {
const HI = "Hi";
const BY = "By";
const NUMBER = 1;
const __default = self::BY;
}
var_dump(new MyEnum(MyEnum::HI));
var_dump(new MyEnum(MyEnum::BY));
//Use __default
var_dump(new MyEnum());
try {
new MyEnum("I don't exist");
} catch (UnexpectedValueException $e) {
var_dump($e->getMessage());
}
輸出結果如下：
object(MyEnum)#1 (2) {
["value":"Enum":private]=>
string(2) "Hi"
["strict":"Enum":private]=>
bool(true)
}
object(MyEnum)#1 (2) {
["value":"Enum":private]=>
string(2) "By"
["strict":"Enum":private]=>
bool(true)
}
object(MyEnum)#1 (2) {
["value":"Enum":private]=>
string(2) "By"
["strict":"Enum":private]=>
bool(true)
}
string(27) "Value is not in enum MyEnum"
希望本文所述對大家PHP程序設計有所幫助。
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