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
下面的Enum类定义是强类型的，使用和定义都很自然。
定义:
class Fruit extends Enum {
static public $APPLE = 1;
static public $ORANGE = 2;
}
Fruit::initialize(); //Can also be called in autoloader
切换Enum
$myFruit = Fruit::$APPLE;
switch ($myFruit) {
case Fruit::$APPLE : echo "I like apples\n"; break;
case Fruit::$ORANGE : echo "I hate oranges\n"; break;
}
>> I like apples
传递Enum作为参数(强类型)
/** Function only accepts Fruit enums as input**/
function echoFruit(Fruit $fruit) {
echo $fruit->getName().": ".$fruit->getValue()."\n";
}
/** Call function with each Enum value that Fruit has */
foreach (Fruit::getList() as $fruit) {
echoFruit($fruit);
}
//Call function with Apple enum
echoFruit(Fruit::$APPLE)
//Will produce an error. This solution is strongly typed
echoFruit(2);
>> APPLE: 1
>> ORANGE: 2
>> APPLE: 1
>> Argument 1 passed to echoFruit() must be an instance of Fruit, integer given
以字符串形式返回Enum
echo "I have an $myFruit\n";
>> I have an APPLE
通过整数获取Enum
$myFruit = Fruit::getByValue(2);
echo "Now I have an $myFruit\n";
>> Now I have an ORANGE
按名称获取Enum
$myFruit = Fruit::getByName("APPLE");
echo "But I definitely prefer an $myFruit\n\n";
>> But I definitely prefer an APPLE
枚举类:
/**
* @author Torge Kummerow
*/
class Enum {
/**
* Holds the values for each type of Enum
*/
static private $list = array();
/**
* Initializes the enum values by replacing the number with an instance of itself
* using reflection
*/
static public function initialize() {
$className = get_called_class();
$class = new ReflectionClass($className);
$staticProperties = $class->getStaticProperties();
self::$list[$className] = array();
foreach ($staticProperties as $propertyName => &$value) {
if ($propertyName == 'list')
continue;
$enum = new $className($propertyName, $value);
$class->setStaticPropertyValue($propertyName, $enum);
self::$list[$className][$propertyName] = $enum;
} unset($value);
}
/**
* Gets the enum for the given value
*
* @param integer $value
* @throws Exception
*
* @return Enum
*/
static public function getByValue($value) {
$className = get_called_class();
foreach (self::$list[$className] as $propertyName=>&$enum) {
/* @var $enum Enum */
if ($enum->value == $value)
return $enum;
} unset($enum);
throw new Exception("No such enum with value=$value of type ".get_called_class());
}
/**
* Gets the enum for the given name
*
* @param string $name
* @throws Exception
*
* @return Enum
*/
static public function getByName($name) {
$className = get_called_class();
if (array_key_exists($name, static::$list[$className]))
return self::$list[$className][$name];
throw new Exception("No such enum ".get_called_class()."::\$$name");
}
/**
* Returns the list of all enum variants
* @return Array of Enum
*/
static public function getList() {
$className = get_called_class();
return self::$list[$className];
}
private $name;
private $value;
public function __construct($name, $value) {
$this->name = $name;
$this->value = $value;
}
public function __toString() {
return $this->name;
}
public function getValue() {
return $this->value;
}
public function getName() {
return $this->name;
}
}
除了
当然，您也可以为ide添加注释
class Fruit extends Enum {
/**
* This comment is for autocomplete support in common IDEs
* @var Fruit A yummy apple
*/
static public $APPLE = 1;
/**
* This comment is for autocomplete support in common IDEs
* @var Fruit A sour orange
*/
static public $ORANGE = 2;
}
//This can also go to the autoloader if available.
Fruit::initialize();
其他回答
class DayOfWeek {
static $values = array(
self::MONDAY,
self::TUESDAY,
// ...
);
const MONDAY = 0;
const TUESDAY = 1;
// ...
}
$today = DayOfWeek::MONDAY;
// If you want to check if a value is valid
assert( in_array( $today, DayOfWeek::$values ) );
不要使用反射。这使得你很难推断你的代码并追踪某些东西被使用的位置，而且往往会破坏静态分析工具(例如你的IDE中内置的工具)。
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。
下面的Enum类定义是强类型的，使用和定义都很自然。
定义:
class Fruit extends Enum {
static public $APPLE = 1;
static public $ORANGE = 2;
}
Fruit::initialize(); //Can also be called in autoloader
切换Enum
$myFruit = Fruit::$APPLE;
switch ($myFruit) {
case Fruit::$APPLE : echo "I like apples\n"; break;
case Fruit::$ORANGE : echo "I hate oranges\n"; break;
}
>> I like apples
传递Enum作为参数(强类型)
/** Function only accepts Fruit enums as input**/
function echoFruit(Fruit $fruit) {
echo $fruit->getName().": ".$fruit->getValue()."\n";
}
/** Call function with each Enum value that Fruit has */
foreach (Fruit::getList() as $fruit) {
echoFruit($fruit);
}
//Call function with Apple enum
echoFruit(Fruit::$APPLE)
//Will produce an error. This solution is strongly typed
echoFruit(2);
>> APPLE: 1
>> ORANGE: 2
>> APPLE: 1
>> Argument 1 passed to echoFruit() must be an instance of Fruit, integer given
以字符串形式返回Enum
echo "I have an $myFruit\n";
>> I have an APPLE
通过整数获取Enum
$myFruit = Fruit::getByValue(2);
echo "Now I have an $myFruit\n";
>> Now I have an ORANGE
按名称获取Enum
$myFruit = Fruit::getByName("APPLE");
echo "But I definitely prefer an $myFruit\n\n";
>> But I definitely prefer an APPLE
枚举类:
/**
* @author Torge Kummerow
*/
class Enum {
/**
* Holds the values for each type of Enum
*/
static private $list = array();
/**
* Initializes the enum values by replacing the number with an instance of itself
* using reflection
*/
static public function initialize() {
$className = get_called_class();
$class = new ReflectionClass($className);
$staticProperties = $class->getStaticProperties();
self::$list[$className] = array();
foreach ($staticProperties as $propertyName => &$value) {
if ($propertyName == 'list')
continue;
$enum = new $className($propertyName, $value);
$class->setStaticPropertyValue($propertyName, $enum);
self::$list[$className][$propertyName] = $enum;
} unset($value);
}
/**
* Gets the enum for the given value
*
* @param integer $value
* @throws Exception
*
* @return Enum
*/
static public function getByValue($value) {
$className = get_called_class();
foreach (self::$list[$className] as $propertyName=>&$enum) {
/* @var $enum Enum */
if ($enum->value == $value)
return $enum;
} unset($enum);
throw new Exception("No such enum with value=$value of type ".get_called_class());
}
/**
* Gets the enum for the given name
*
* @param string $name
* @throws Exception
*
* @return Enum
*/
static public function getByName($name) {
$className = get_called_class();
if (array_key_exists($name, static::$list[$className]))
return self::$list[$className][$name];
throw new Exception("No such enum ".get_called_class()."::\$$name");
}
/**
* Returns the list of all enum variants
* @return Array of Enum
*/
static public function getList() {
$className = get_called_class();
return self::$list[$className];
}
private $name;
private $value;
public function __construct($name, $value) {
$this->name = $name;
$this->value = $value;
}
public function __toString() {
return $this->name;
}
public function getValue() {
return $this->value;
}
public function getName() {
return $this->name;
}
}
除了
当然，您也可以为ide添加注释
class Fruit extends Enum {
/**
* This comment is for autocomplete support in common IDEs
* @var Fruit A yummy apple
*/
static public $APPLE = 1;
/**
* This comment is for autocomplete support in common IDEs
* @var Fruit A sour orange
*/
static public $ORANGE = 2;
}
//This can also go to the autoloader if available.
Fruit::initialize();
abstract class Enumeration
{
public static function enum()
{
$reflect = new ReflectionClass( get_called_class() );
return $reflect->getConstants();
}
}
class Test extends Enumeration
{
const A = 'a';
const B = 'b';
}
foreach (Test::enum() as $key => $value) {
echo "$key -> $value<br>";
}
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];
}
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