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  • php闭包使用例子

    一.依据闭包实现一个容器

    class Di
    {
        private $factory;
    
        public function set($id, $value)
        {
            $this->factory[$id] = $value;
        }
    
        public function get($id)
        {
            $val = $this->factory[$id];
            return $val();//如果不加括号,仅仅返回的是闭包类,并不是User实例
        }
    }
    
    class User
    {
        private $username;
    
        public function __construct($username = '')
        {
            $this->username = $username;
        }
    
        public function getUserName()
        {
            return $this->username;
        }
    }
    
    $di = new Di();
    
    // 在此使用了闭包,所以实际上并不会实例化User类,只有在后面get的时候才会实例化
    $di->set('a', function(){
        return new User('张三');
    });
    
    var_dump($di->get('a')->getUserName());
    

      

    二.使用闭包作为回调

    class Cart
    {
        CONST PRICE_BUTTER = 1.0;
        CONST PRICE_MILK = 5.05;
    
        protected $products = [];
    
        public function add($product, $quantity)
        {
            $this->products[$product] = $quantity;
        }
    
        public function getQuantity($product)
        {
            return isset($this->products[$product]) ? $this->products[$product]: false;
        }
    
        public function getTotal($tax)
        {
            $total = 0.00;
            $callback = function($quantity, $product) use ($tax, &$total) {
                $priceItem = constant(__CLASS__ . '::PRICE_' . strtoupper($product));
                $total += ($priceItem * $quantity) * ($tax + 1.0);
            };
    
            array_walk($this->products, $callback);
            return round($total, 2);
        }
    }
    
    $cart = new Cart();
    $cart->add('butter', 1);
    $cart->add('milk', 5);
    
    echo $cart->getTotal(0.05);
    

      

     三.使用闭包函数调用类中方法

    class Grid
    {
        protected $builder;
        protected $attribute;
    
        public function __construct(Closure $builler)
        {
            $this->builder = $builler;
        }
    
        public function addColumn($name, $value)
        {
            $this->attribute[$name] = $value;
            return $this;
        }
    
        public function build()
        {
            // 这儿回调闭包函数,参数为this
            call_user_func($this->builder, $this);
        }
    
        public function __toString()
        {
            $this->build();
    
            $str = '';
            $call = function($val, $key) use(&$str) {
                 $str .= "$key=>$val;";
            };
            array_walk($this->attribute, $call);
    
            return $str;
        }
    }
    
    $grid = new Grid(
        // 传入闭包函数,带参数
        function($grid) {
            $grid->addColumn('key1', 'val1');
            $grid->addColumn('key2', 'val2');
        }
    );
    
    echo $grid;
    

      

    闭包在对象中的一个典型使用场景就是留出一个方法给调用者,让调用者自主决定或组装数据.
    如下例:让调用者决定如何组装或显示info.

    class CalledClass {
        private $name;
        private $age;
        private $info;
    
        public function __construct($name, $age, Closure $callable)
        {
            $this->name = $name;
            $this->age = $age;
            call_user_func($callable, $this);
            // 这相当于
            // $callable($this);
        }
    
        public function setInfo($info)
        {
            $this->info = $info;
        }
    
        public function getInfo()
        {
            echo $this->info;
        }
    
        /**
         * @return mixed
         */
        public function getName()
        {
            return $this->name;
        }
    
        /**
         * @return mixed
         */
        public function getAge()
        {
            return $this->age;
        }
    
    
    }
    
    $c = new CalledClass('php', 10, function (CalledClass $c) {
        echo $c->getAge() . $c->getName();
        $c->setInfo($c->getAge() . $c->getName());
    });
    
    echo $c->getInfo();
    

      

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  • 原文地址:https://www.cnblogs.com/itfenqing/p/7073307.html
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