js30--代理模式

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

<html>

    <head>

        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

        <title>Untitled Document</title>

        <script type=text/javascript charset=utf-8 src=../commons/CommonUtil.js ></script>

        <script type=text/javascript charset=utf-8>

                //代理模式（proxy）：代理也是对象，他的目的就是为了节制（控制）对本体对象的访问

                var LibraryInterface = new BH.Interface('LibraryInterface' ,['addbook','findbook','checkoutbook','returnbook']);

                var Book = function(id , title , author){

                    this.id = id;

                    this.title = title ;

                    this.author = author;

                };

                //图书馆(本体对象 , 实例化图书馆需要消耗很多的资源)

                var Library = function(books){

                    this.books = books;//{bookid : book}

                };

                Library.prototype = {

                    constructor:Library ,

                    addbook:function(book){

                        this.books[book.id] = book;//访问json用中括号

                    },

                    findbook:function(id){

                        if(this.books[id]){

                            return this.books[id];

                        }

                        return null;

                    },

                    checkoutbook:function(id){

                        //电脑登记..交押金

                        return this.findbook(id);

                    },

                    returnbook:function(book){

                        //电脑登记(...已还)

                        //计算费用(计算余额)

                        this.books[book.id] = book;

                    }

                };

                //图书馆的代理对象

                var LibraryProxy = function(books){

                    alert('产生代理对象，但是并没有产生真正的本体对象!');

                    this.books = books;

                    this.library = null; //定义一个空对象

                };

                LibraryProxy.prototype = {

                    constructor:LibraryProxy ,

                    initializeLibrary:function(){

                        if(this.library == null){

                            alert('真正的本体对象!');

                            this.library = new Library(this.books);

                        }

                    },

                    addbook:function(book){

                        this.initializeLibrary();

                        //实际上具体做事情的还是本体对象自己本身

                        this.library.addbook(book);

                    },

                    findbook:function(id){

                        this.initializeLibrary();

                        return this.library.findbook(id);

                    },

                    checkoutbook:function(id){

                        this.initializeLibrary();

                        return this.findbook(id);

                    },

                    returnbook:function(book){

                        this.initializeLibrary();

                        this.library.returnbook(book);

                    }

                };                

                //实例化的是代理对象：推迟本体对象实例化的时间，什么时候具体去做事情了，再去实例化它

                // hibernate： get(全查询出来)   load(返回代理对象)

                var proxy = new LibraryProxy({

                    "01":new Book('01','java','z3'),

                    "02":new Book('02','js','z4')

                });

                alert(proxy.findbook('01').title);

        </script>

    </head>

    <body>

    </body>

</html>
巴特西

js30--代理模式

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