PHP方法链接？

时间：2010-09-16 06:04:37

标签： php oop method-chaining

我正在使用PHP 5，我听说过面向对象方法中的一个新功能，称为“方法链”。究竟是什么？我该如何实现它？

10 个答案:

答案 0 :(得分：302)

它非常简单，你有一系列mutator methods，它们都返回原始（或其他）对象，这样你就可以继续在返回的对象上调用方法。

<?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();

输出“ab”

Try it online!

答案 1 :(得分：42)

基本上，你拿一个物体：

$obj = new ObjectWithChainableMethods();

调用最终有效执行return $this;的方法：

$obj->doSomething();

由于它将同一个对象，或者更确切地说，引用返回给同一个对象，因此可以继续从返回值中调用同一类的方法，如下所示：

$obj->doSomething()->doSomethingElse();

就是这样，真的。两件重要的事情：

  1. 正如您所说，它只是PHP 5。它在PHP 4中无法正常工作，因为它按值返回对象，这意味着您在对象的不同副本上调用方法，这会破坏您的代码。

  2. 同样，您需要在可链接方法中返回对象：

    public function doSomething() {
    // Do stuff
    return $this;
}

public function doSomethingElse() {
    // Do more stuff
    return $this;
}

答案 2 :(得分：24)

试试这段代码：

<?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'

?>

答案 3 :(得分：10)

方法链接意味着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（）则给出了method1（）的结果。然后，Method2（）将返回值传递给method3（）。

好文章：http://www.talkphp.com/advanced-php-programming/1163-php5-method-chaining.html

答案 4 :(得分：7)

静态方法链的另一种方法：

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);
    }    
}

调用

echo Maker::words(['foo', 'bob', 'bar'])->concate('-')->get();

echo "<br />";

echo Maker::words(['foo', 'bob', 'bar'])->concate('>')->get();

答案 5 :(得分：6)

有49行代码允许您将方法链接到这样的数组：

$fruits = new Arr(array("lemon", "orange", "banana", "apple"));
$fruits->change_key_case(CASE_UPPER)->filter()->walk(function($value,$key) {
     echo $key.': '.$value."\r\n";
});

参见这篇文章，向您展示如何链接所有PHP的70个array_函数。

http://domexception.blogspot.fi/2013/08/php-magic-methods-and-arrayobject.html

答案 6 :(得分：1)

流畅的界面使您可以链接方法调用，从而在对同一对象执行多项操作时减少了键入的字符。

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;

答案 7 :(得分：0)

我认为这是最相关的答案。

import 'package:flutter/material.dart';

import 'package:flutter/widgets.dart';

void main() => runApp(MyApp());

/// This Widget is the main application widget.
class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: Center(
          child: MyStatefulWidget(),
        ),
      ),
    );
  }
}

class MyStatefulWidget extends StatefulWidget {
  MyStatefulWidget({Key key}) : super(key: key);

  @override
  _MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  Color textColor = Colors.blue;
  int _enterCounter = 0;
  int _exitCounter = 0;
  double x = 0.0;
  double y = 0.0;

  void _incrementEnter(PointerEvent details) {
    setState(() {
      _enterCounter++;
    });
  }

  void _incrementExit(PointerEvent details) {
    setState(() {
      textColor = Colors.blue;
      _exitCounter++;
    });
  }

  void _updateLocation(PointerEvent details) {
    setState(() {
      textColor = Colors.red;
      x = details.position.dx;
      y = details.position.dy;
    });
  }


  @override
  Widget build(BuildContext context) {
    return MouseRegion(
      onEnter: _incrementEnter,
      onHover: _updateLocation,
      onExit: _incrementExit,
      child: FlatButton(
        color: Colors.white,
        textColor: Colors.teal[700], //when hovered text color change
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(5),
          side: BorderSide(
            color: Colors.teal[700],
          ),
        ),
        onPressed: () {},
        child: Text("Log in", style: TextStyle(color: textColor),),
      ),
    );
  }
}

答案 8 :(得分：-1)

以下是我的模型，可以通过数据库中的ID找到。 with（$ data）方法是我关系的附加参数，所以我返回$ this，它就是对象本身。在我的控制器上，我可以链接它。

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);
    }
}

答案 9 :(得分：-1)

如果你的意思是方法链接就像在JavaScript中（或者有些人记住jQuery），为什么不采取带来该开发的库。 PHP的经验？例如Extras - https://dsheiko.github.io/extras/这个使用JavaScript和Underscore方法扩展PHP类型并提供链接：

您可以链接特定类型：

<?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

<?php
use \Dsheiko\Extras\Strings;
$res = Strings::from( " 12345 " )
            ->replace("/1/", "5")
            ->replace("/2/", "5")
            ->trim()
            ->substr(1, 3)
            ->get();
echo $res; // "534"

或者你可以去多态：

<?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"
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