我知道PHP还没有本地枚举。但是我已经习惯了来自Java世界的它们。我喜欢使用枚举来提供ide的自动补全功能能够理解的预定义值。
常量可以解决这个问题,但是存在名称空间冲突问题,而且(实际上是因为)它们是全局的。数组没有名称空间的问题,但是它们太模糊了,它们可以在运行时被覆盖,而且ide很少知道如何在没有额外的静态分析注释或属性的情况下自动填充它们的键。
你有什么常用的解决方案/变通办法吗?有人记得PHP的人对枚举有什么想法或决定吗?
我知道PHP还没有本地枚举。但是我已经习惯了来自Java世界的它们。我喜欢使用枚举来提供ide的自动补全功能能够理解的预定义值。
常量可以解决这个问题,但是存在名称空间冲突问题,而且(实际上是因为)它们是全局的。数组没有名称空间的问题,但是它们太模糊了,它们可以在运行时被覆盖,而且ide很少知道如何在没有额外的静态分析注释或属性的情况下自动填充它们的键。
你有什么常用的解决方案/变通办法吗?有人记得PHP的人对枚举有什么想法或决定吗?
当前回答
踩在布莱恩·克莱恩的回答上,我想我可能会给出我的5美分
<?php
/**
* A class that simulates Enums behaviour
* <code>
* class Season extends Enum{
* const Spring = 0;
* const Summer = 1;
* const Autumn = 2;
* const Winter = 3;
* }
*
* $currentSeason = new Season(Season::Spring);
* $nextYearSeason = new Season(Season::Spring);
* $winter = new Season(Season::Winter);
* $whatever = new Season(-1); // Throws InvalidArgumentException
* echo $currentSeason.is(Season::Spring); // True
* echo $currentSeason.getName(); // 'Spring'
* echo $currentSeason.is($nextYearSeason); // True
* echo $currentSeason.is(Season::Winter); // False
* echo $currentSeason.is(Season::Spring); // True
* echo $currentSeason.is($winter); // False
* </code>
*
* Class Enum
*
* PHP Version 5.5
*/
abstract class Enum
{
/**
* Will contain all the constants of every enum that gets created to
* avoid expensive ReflectionClass usage
* @var array
*/
private static $_constCacheArray = [];
/**
* The value that separates this instance from the rest of the same class
* @var mixed
*/
private $_value;
/**
* The label of the Enum instance. Will take the string name of the
* constant provided, used for logging and human readable messages
* @var string
*/
private $_name;
/**
* Creates an enum instance, while makes sure that the value given to the
* enum is a valid one
*
* @param mixed $value The value of the current
*
* @throws \InvalidArgumentException
*/
public final function __construct($value)
{
$constants = self::_getConstants();
if (count($constants) !== count(array_unique($constants))) {
throw new \InvalidArgumentException('Enums cannot contain duplicate constant values');
}
if ($name = array_search($value, $constants)) {
$this->_value = $value;
$this->_name = $name;
} else {
throw new \InvalidArgumentException('Invalid enum value provided');
}
}
/**
* Returns the constant name of the current enum instance
*
* @return string
*/
public function getName()
{
return $this->_name;
}
/**
* Returns the value of the current enum instance
*
* @return mixed
*/
public function getValue()
{
return $this->_value;
}
/**
* Checks whether this enum instance matches with the provided one.
* This function should be used to compare Enums at all times instead
* of an identity comparison
* <code>
* // Assuming EnumObject and EnumObject2 both extend the Enum class
* // and constants with such values are defined
* $var = new EnumObject('test');
* $var2 = new EnumObject('test');
* $var3 = new EnumObject2('test');
* $var4 = new EnumObject2('test2');
* echo $var->is($var2); // true
* echo $var->is('test'); // true
* echo $var->is($var3); // false
* echo $var3->is($var4); // false
* </code>
*
* @param mixed|Enum $enum The value we are comparing this enum object against
* If the value is instance of the Enum class makes
* sure they are instances of the same class as well,
* otherwise just ensures they have the same value
*
* @return bool
*/
public final function is($enum)
{
// If we are comparing enums, just make
// sure they have the same toString value
if (is_subclass_of($enum, __CLASS__)) {
return get_class($this) === get_class($enum)
&& $this->getValue() === $enum->getValue();
} else {
// Otherwise assume $enum is the value we are comparing against
// and do an exact comparison
return $this->getValue() === $enum;
}
}
/**
* Returns the constants that are set for the current Enum instance
*
* @return array
*/
private static function _getConstants()
{
if (self::$_constCacheArray == null) {
self::$_constCacheArray = [];
}
$calledClass = get_called_class();
if (!array_key_exists($calledClass, self::$_constCacheArray)) {
$reflect = new \ReflectionClass($calledClass);
self::$_constCacheArray[$calledClass] = $reflect->getConstants();
}
return self::$_constCacheArray[$calledClass];
}
}
其他回答
我知道这是一个旧线程,然而没有一个我所见过的解决方法真的看起来像枚举,因为几乎所有的解决方法都需要你手动分配值给枚举项,或者它需要你传递一个枚举键数组到一个函数。所以我创造了自己的解决方案。
要使用我的解决方案创建枚举类,可以简单地扩展下面的enum类,创建一堆静态变量(不需要初始化它们),并在枚举类定义的下面调用yourEnumClass::init()。
edit: This only works in php >= 5.3, but it can probably be modified to work in older versions as well /** * A base class for enums. * * This class can be used as a base class for enums. * It can be used to create regular enums (incremental indices), but it can also be used to create binary flag values. * To create an enum class you can simply extend this class, and make a call to <yourEnumClass>::init() before you use the enum. * Preferably this call is made directly after the class declaration. * Example usages: * DaysOfTheWeek.class.php * abstract class DaysOfTheWeek extends Enum{ * static $MONDAY = 1; * static $TUESDAY; * static $WEDNESDAY; * static $THURSDAY; * static $FRIDAY; * static $SATURDAY; * static $SUNDAY; * } * DaysOfTheWeek::init(); * * example.php * require_once("DaysOfTheWeek.class.php"); * $today = date('N'); * if ($today == DaysOfTheWeek::$SUNDAY || $today == DaysOfTheWeek::$SATURDAY) * echo "It's weekend!"; * * Flags.class.php * abstract class Flags extends Enum{ * static $FLAG_1; * static $FLAG_2; * static $FLAG_3; * } * Flags::init(Enum::$BINARY_FLAG); * * example2.php * require_once("Flags.class.php"); * $flags = Flags::$FLAG_1 | Flags::$FLAG_2; * if ($flags & Flags::$FLAG_1) * echo "Flag_1 is set"; * * @author Tiddo Langerak */ abstract class Enum{ static $BINARY_FLAG = 1; /** * This function must be called to initialize the enumeration! * * @param bool $flags If the USE_BINARY flag is provided, the enum values will be binary flag values. Default: no flags set. */ public static function init($flags = 0){ //First, we want to get a list of all static properties of the enum class. We'll use the ReflectionClass for this. $enum = get_called_class(); $ref = new ReflectionClass($enum); $items = $ref->getStaticProperties(); //Now we can start assigning values to the items. if ($flags & self::$BINARY_FLAG){ //If we want binary flag values, our first value should be 1. $value = 1; //Now we can set the values for all items. foreach ($items as $key=>$item){ if (!isset($item)){ //If no value is set manually, we should set it. $enum::$$key = $value; //And we need to calculate the new value $value *= 2; } else { //If there was already a value set, we will continue starting from that value, but only if that was a valid binary flag value. //Otherwise, we will just skip this item. if ($key != 0 && ($key & ($key - 1) == 0)) $value = 2 * $item; } } } else { //If we want to use regular indices, we'll start with index 0. $value = 0; //Now we can set the values for all items. foreach ($items as $key=>$item){ if (!isset($item)){ //If no value is set manually, we should set it, and increment the value for the next item. $enum::$$key = $value; $value++; } else { //If a value was already set, we'll continue from that value. $value = $item+1; } } } } }
上面的答案太棒了。但是,如果以两种不同的方式进行扩展,那么无论先进行哪种扩展,都会导致对函数的调用,从而创建缓存。这个缓存将被所有后续调用使用,无论调用是由哪个扩展发起的…
要解决这个问题,将变量和第一个函数替换为:
private static $constCacheArray = null;
private static function getConstants() {
if (self::$constCacheArray === null) self::$constCacheArray = array();
$calledClass = get_called_class();
if (!array_key_exists($calledClass, self::$constCacheArray)) {
$reflect = new \ReflectionClass($calledClass);
self::$constCacheArray[$calledClass] = $reflect->getConstants();
}
return self::$constCacheArray[$calledClass];
}
我试图用PHP创建一个枚举…这是非常有限的,因为它不支持对象作为枚举值,但仍然有点有用…
class ProtocolsEnum {
const HTTP = '1';
const HTTPS = '2';
const FTP = '3';
/**
* Retrieve an enum value
* @param string $name
* @return string
*/
public static function getValueByName($name) {
return constant('self::'. $name);
}
/**
* Retrieve an enum key name
* @param string $code
* @return string
*/
public static function getNameByValue($code) {
foreach(get_class_constants() as $key => $val) {
if($val == $code) {
return $key;
}
}
}
/**
* Retrieve associate array of all constants (used for creating droplist options)
* @return multitype:
*/
public static function toArray() {
return array_flip(self::get_class_constants());
}
private static function get_class_constants()
{
$reflect = new ReflectionClass(__CLASS__);
return $reflect->getConstants();
}
}
好吧,对于一个简单的java,比如php中的enum,我使用:
class SomeTypeName {
private static $enum = array(1 => "Read", 2 => "Write");
public function toOrdinal($name) {
return array_search($name, self::$enum);
}
public function toString($ordinal) {
return self::$enum[$ordinal];
}
}
我们称它为:
SomeTypeName::toOrdinal("Read");
SomeTypeName::toString(1);
但我是PHP初学者,语法不好,所以这可能不是最好的方法。我尝试了一些类常量,使用反射从它的值中获得常量名,可能更整洁。
我所见过的PHP中枚举最常见的解决方案是创建一个通用枚举类,然后扩展它。你可以看看这个。
更新:或者,我从phpclasses.org找到了这个。