我正在使用PHP 5,我听说面向对象编程中有一种新的特性叫做“方法链”,那是什么?如何实现它?
我正在使用PHP 5,我听说面向对象编程中有一种新的特性叫做“方法链”,那是什么?如何实现它?
其实很简单。你有一系列的变异器方法,它们都返回原始(或其他)对象。这样,你就可以在返回的对象上继续调用方法。
<?php
class fakeString
{
private $str;
function __construct()
{
$this->str = "";
}
function addA()
{
$this->str .= "a";
return $this;
}
function addB()
{
$this->str .= "b";
return $this;
}
function getStr()
{
return $this->str;
}
}
$a = new fakeString();
echo $a->addA()->addB()->getStr();
这会输出“ab”
$foo->setBar(1)->setBaz(2)
与$table->select()->from('foo')->where('bar = 1')->order('ASC)
。后者涉及多个对象。 - Gordon$a = (new fakeString())->addA()->addB()->getStr();
- Philzen基本上,你需要取一个对象:
$obj = new ObjectWithChainableMethods();
调用一个方法,该方法在末尾有效地执行 return $this;
:
$obj->doSomething();
由于它返回相同的对象,或者更确切地说,是对相同对象的引用,因此您可以继续通过返回值调用同一类的方法,例如:
$obj->doSomething()->doSomethingElse();
就这样了,有两个重要的事情:
正如你所提到的,它只适用于PHP 5。在PHP 4中不会正常工作,因为它按值返回对象,这意味着您正在调用不同副本的对象上的方法,这将破坏您的代码。
同样,在可链接的方法中需要返回对象:
public function doSomething() {
// Do stuff
return $this;
}
public function doSomethingElse() {
// Do more stuff
return $this;
}
return &$this
吗? - alex尝试这段代码:
<?php
class DBManager
{
private $selectables = array();
private $table;
private $whereClause;
private $limit;
public function select() {
$this->selectables = func_get_args();
return $this;
}
public function from($table) {
$this->table = $table;
return $this;
}
public function where($where) {
$this->whereClause = $where;
return $this;
}
public function limit($limit) {
$this->limit = $limit;
return $this;
}
public function result() {
$query[] = "SELECT";
// if the selectables array is empty, select all
if (empty($this->selectables)) {
$query[] = "*";
}
// else select according to selectables
else {
$query[] = join(', ', $this->selectables);
}
$query[] = "FROM";
$query[] = $this->table;
if (!empty($this->whereClause)) {
$query[] = "WHERE";
$query[] = $this->whereClause;
}
if (!empty($this->limit)) {
$query[] = "LIMIT";
$query[] = $this->limit;
}
return join(' ', $query);
}
}
// Now to use the class and see how METHOD CHAINING works
// let us instantiate the class DBManager
$testOne = new DBManager();
$testOne->select()->from('users');
echo $testOne->result();
// OR
echo $testOne->select()->from('users')->result();
// both displays: 'SELECT * FROM users'
$testTwo = new DBManager();
$testTwo->select()->from('posts')->where('id > 200')->limit(10);
echo $testTwo->result();
// this displays: 'SELECT * FROM posts WHERE id > 200 LIMIT 10'
$testThree = new DBManager();
$testThree->select(
'firstname',
'email',
'country',
'city'
)->from('users')->where('id = 2399');
echo $testThree->result();
// this will display:
// 'SELECT firstname, email, country, city FROM users WHERE id = 2399'
?>
class Maker
{
private static $result = null;
private static $delimiter = '.';
private static $data = [];
public static function words($words)
{
if( !empty($words) && count($words) )
{
foreach ($words as $w)
{
self::$data[] = $w;
}
}
return new static;
}
public static function concate($delimiter)
{
self::$delimiter = $delimiter;
foreach (self::$data as $d)
{
self::$result .= $d.$delimiter;
}
return new static;
}
public static function get()
{
return rtrim(self::$result, self::$delimiter);
}
}
echo Maker::words(['foo', 'bob', 'bar'])->concate('-')->get();
echo "<br />";
echo Maker::words(['foo', 'bob', 'bar'])->concate('>')->get();
方法链是指您可以链接方法调用:
$object->method1()->method2()->method3()
这意味着method1()需要返回一个对象,而method2()得到了method1()的结果。然后,method2()将返回值传递给method3()。以下是49行代码,可让您像这样在数组上链接方法:
$fruits = new Arr(array("lemon", "orange", "banana", "apple"));
$fruits->change_key_case(CASE_UPPER)->filter()->walk(function($value,$key) {
echo $key.': '.$value."\r\n";
});
流畅接口允许您链接方法调用,这样在对同一对象应用多个操作时就会减少输入的字符数。
class Bill {
public $dinner = 20;
public $desserts = 5;
public $bill;
public function dinner( $person ) {
$this->bill += $this->dinner * $person;
return $this;
}
public function dessert( $person ) {
$this->bill += $this->desserts * $person;
return $this;
}
}
$bill = new Bill();
echo $bill->dinner( 2 )->dessert( 3 )->bill;
我认为这是最相关的答案。
<?php
class Calculator
{
protected $result = 0;
public function sum($num)
{
$this->result += $num;
return $this;
}
public function sub($num)
{
$this->result -= $num;
return $this;
}
public function result()
{
return $this->result;
}
}
$calculator = new Calculator;
echo $calculator->sum(10)->sub(5)->sum(3)->result(); // 8
<?php
use \Dsheiko\Extras\Arrays;
// Chain of calls
$res = Arrays::chain([1, 2, 3])
->map(function($num){ return $num + 1; })
->filter(function($num){ return $num > 1; })
->reduce(function($carry, $num){ return $carry + $num; }, 0)
->value();
或者
<?php
use \Dsheiko\Extras\Strings;
$res = Strings::from( " 12345 " )
->replace("/1/", "5")
->replace("/2/", "5")
->trim()
->substr(1, 3)
->get();
echo $res; // "534"
或者您可以选择多态:
<?php
use \Dsheiko\Extras\Any;
$res = Any::chain(new \ArrayObject([1,2,3]))
->toArray() // value is [1,2,3]
->map(function($num){ return [ "num" => $num ]; })
// value is [[ "num" => 1, ..]]
->reduce(function($carry, $arr){
$carry .= $arr["num"];
return $carry;
}, "") // value is "123"
->replace("/2/", "") // value is "13"
->then(function($value){
if (empty($value)) {
throw new \Exception("Empty value");
}
return $value;
})
->value();
echo $res; // "13"
class JobModel implements JobInterface{
protected $job;
public function __construct(Model $job){
$this->job = $job;
}
public function find($id){
return $this->job->find($id);
}
public function with($data=[]){
$this->job = $this->job->with($params);
return $this;
}
}
class JobController{
protected $job;
public function __construct(JobModel $job){
$this->job = $job;
}
public function index(){
// chaining must be in order
$this->job->with(['data'])->find(1);
}
}