你不能在一个PHP类中放入两个具有唯一参数签名的__construct函数。我想这样做:
class Student
{
protected $id;
protected $name;
// etc.
public function __construct($id){
$this->id = $id;
// other members are still uninitialized
}
public function __construct($row_from_database){
$this->id = $row_from_database->id;
$this->name = $row_from_database->name;
// etc.
}
}
PHP中最好的方法是什么?
当前回答
对于php7，我也比较了参数类型，你可以有两个具有相同数量的参数但不同类型的构造函数。
trait GenericConstructorOverloadTrait
{
/**
* @var array Constructors metadata
*/
private static $constructorsCache;
/**
* Generic constructor
* GenericConstructorOverloadTrait constructor.
*/
public function __construct()
{
$params = func_get_args();
$numParams = func_num_args();
$finish = false;
if(!self::$constructorsCache){
$class = new \ReflectionClass($this);
$constructors = array_filter($class->getMethods(),
function (\ReflectionMethod $method) {
return preg_match("/\_\_construct[0-9]+/",$method->getName());
});
self::$constructorsCache = $constructors;
}
else{
$constructors = self::$constructorsCache;
}
foreach($constructors as $constructor){
$reflectionParams = $constructor->getParameters();
if(count($reflectionParams) != $numParams){
continue;
}
$matched = true;
for($i=0; $i< $numParams; $i++){
if($reflectionParams[$i]->hasType()){
$type = $reflectionParams[$i]->getType()->__toString();
}
if(
!(
!$reflectionParams[$i]->hasType() ||
($reflectionParams[$i]->hasType() &&
is_object($params[$i]) &&
$params[$i] instanceof $type) ||
($reflectionParams[$i]->hasType() &&
$reflectionParams[$i]->getType()->__toString() ==
gettype($params[$i]))
)
) {
$matched = false;
break;
}
}
if($matched){
call_user_func_array(array($this,$constructor->getName()),
$params);
$finish = true;
break;
}
}
unset($constructor);
if(!$finish){
throw new \InvalidArgumentException("Cannot match construct by params");
}
}
}
使用它:
class MultiConstructorClass{
use GenericConstructorOverloadTrait;
private $param1;
private $param2;
private $param3;
public function __construct1($param1, array $param2)
{
$this->param1 = $param1;
$this->param2 = $param2;
}
public function __construct2($param1, array $param2, \DateTime $param3)
{
$this->__construct1($param1, $param2);
$this->param3 = $param3;
}
/**
* @return \DateTime
*/
public function getParam3()
{
return $this->param3;
}
/**
* @return array
*/
public function getParam2()
{
return $this->param2;
}
/**
* @return mixed
*/
public function getParam1()
{
return $this->param1;
}
}
其他回答
为了回应Kris的最佳答案(顺便说一句，他帮助我设计了自己的课程)，这里有一个修改过的版本，供那些可能会觉得有用的人使用。包括用于从任何列中进行选择和从数组中转储对象数据的方法。干杯!
public function __construct() {
$this -> id = 0;
//...
}
public static function Exists($id) {
if (!$id) return false;
$id = (int)$id;
if ($id <= 0) return false;
$mysqli = Mysql::Connect();
if (mysqli_num_rows(mysqli_query($mysqli, "SELECT id FROM users WHERE id = " . $id)) == 1) return true;
return false;
}
public static function FromId($id) {
$u = new self();
if (!$u -> FillFromColumn("id", $id)) return false;
return $u;
}
public static function FromColumn($column, $value) {
$u = new self();
if (!$u -> FillFromColumn($column, $value)) return false;
return $u;
}
public static function FromArray($row = array()) {
if (!is_array($row) || $row == array()) return false;
$u = new self();
$u -> FillFromArray($row);
return $u;
}
protected function FillFromColumn($column, $value) {
$mysqli = Mysql::Connect();
//Assuming we're only allowed to specified EXISTENT columns
$result = mysqli_query($mysqli, "SELECT * FROM users WHERE " . $column . " = '" . $value . "'");
$count = mysqli_num_rows($result);
if ($count == 0) return false;
$row = mysqli_fetch_assoc($result);
$this -> FillFromArray($row);
}
protected function FillFromArray(array $row) {
foreach($row as $i => $v) {
if (isset($this -> $i)) {
$this -> $i = $v;
}
}
}
public function ToArray() {
$m = array();
foreach ($this as $i => $v) {
$m[$i] = $v;
}
return $m;
}
public function Dump() {
print_r("<PRE>");
print_r($this -> ToArray());
print_r("</PRE>");
}
从5.4版开始，PHP支持trait。这并不是你真正想要的，但基于特征的简单方法是:
trait StudentTrait {
protected $id;
protected $name;
final public function setId($id) {
$this->id = $id;
return $this;
}
final public function getId() { return $this->id; }
final public function setName($name) {
$this->name = $name;
return $this;
}
final public function getName() { return $this->name; }
}
class Student1 {
use StudentTrait;
final public function __construct($id) { $this->setId($id); }
}
class Student2 {
use StudentTrait;
final public function __construct($id, $name) { $this->setId($id)->setName($name); }
}
我们最终得到两个类，每个构造函数一个，这有点适得其反。为了保持理智，我将加入一个工厂:
class StudentFactory {
static public function getStudent($id, $name = null) {
return
is_null($name)
? new Student1($id)
: new Student2($id, $name)
}
}
所以，这一切都归结为:
$student1 = StudentFactory::getStudent(1);
$student2 = StudentFactory::getStudent(1, "yannis");
这是一个非常冗长的方法，但它可以非常方便。
你可以像下面这样做，非常简单明了:
public function __construct()
{
$arguments = func_get_args();
switch(sizeof(func_get_args()))
{
case 0: //No arguments
break;
case 1: //One argument
$this->do_something($arguments[0]);
break;
case 2: //Two arguments
$this->do_something_else($arguments[0], $arguments[1]);
break;
}
}
更现代的方法: 你把独立的类混合成一个，实体和数据水合。 对于你的案例，你应该有两个类:
class Student
{
protected $id;
protected $name;
// etc.
}
class StudentHydrator
{
public function hydrate(Student $student, array $data){
$student->setId($data['id']);
if(isset($data['name')){
$student->setName($data['name']);
}
// etc. Can be replaced with foreach
return $student;
}
}
//usage
$hydrator = new StudentHydrator();
$student = $hydrator->hydrate(new Student(), ['id'=>4]);
$student2 = $hydrator->hydrate(new Student(), $rowFromDB);
另外请注意，您应该使用doctrine或其他已经提供自动实体水合的ORM。 你应该使用依赖注入来跳过手动创建像StudentHydrator这样的对象。
这是我对它的看法(为php 5.6构建)。
它将查看构造函数参数类型(数组，类名，无描述)并比较给定的参数。构造函数必须在最后以最少的特异性给出。例子:
// demo class
class X {
public $X;
public function __construct($x) {
$this->X = $x;
}
public function __toString() {
return 'X'.$this->X;
}
}
// demo class
class Y {
public $Y;
public function __construct($y) {
$this->Y = $y;
}
public function __toString() {
return 'Y'.$this->Y;
}
}
// here be magic
abstract class MultipleConstructors {
function __construct() {
$__get_arguments = func_get_args();
$__number_of_arguments = func_num_args();
$__reflect = new ReflectionClass($this);
foreach($__reflect->getMethods() as $__reflectmethod) {
$__method_name = $__reflectmethod->getName();
if (substr($__method_name, 0, strlen('__construct')) === '__construct') {
$__parms = $__reflectmethod->getParameters();
if (count($__parms) == $__number_of_arguments) {
$__argsFit = true;
foreach ($__parms as $__argPos => $__param) {
$__paramClass= $__param->getClass();
$__argVar = func_get_arg($__argPos);
$__argVarType = gettype($__argVar);
$__paramIsArray = $__param->isArray() == true;
$__argVarIsArray = $__argVarType == 'array';
// parameter is array and argument isn't, or the other way around.
if (($__paramIsArray && !$__argVarIsArray) ||
(!$__paramIsArray && $__argVarIsArray)) {
$__argsFit = false;
continue;
}
// class check
if ((!is_null($__paramClass) && $__argVarType != 'object') ||
(is_null($__paramClass) && $__argVarType == 'object')){
$__argsFit = false;
continue;
}
if (!is_null($__paramClass) && $__argVarType == 'object') {
// class type check
$__paramClassName = "N/A";
if ($__paramClass)
$__paramClassName = $__paramClass->getName();
if ($__paramClassName != get_class($__argVar)) {
$__argsFit = false;
}
}
}
if ($__argsFit) {
call_user_func_array(array($this, $__method_name), $__get_arguments);
return;
}
}
}
}
throw new Exception("No matching constructors");
}
}
// how to use multiple constructors
class A extends MultipleConstructors {
public $value;
function __constructB(array $hey) {
$this->value = 'Array#'.count($hey).'<br/>';
}
function __construct1(X $first) {
$this->value = $first .'<br/>';
}
function __construct2(Y $second) {
$this->value = $second .'<br/>';
}
function __constructA($hey) {
$this->value = $hey.'<br/>';
}
function __toString() {
return $this->value;
}
}
$x = new X("foo");
$y = new Y("bar");
$aa = new A(array("one", "two", "three"));
echo $aa;
$ar = new A("baz");
echo $ar;
$ax = new A($x);
echo $ax;
$ay = new A($y);
echo $ay;
结果:
Array#3
baz
Xfoo
Ybar
如果没有找到构造函数，可以将其删除并允许构造函数为“空”，而不是终止异常。或者你喜欢什么都行。
