探究javascript mvc(二)

1.问题

该实现方式很好的实现了所有要求的功能，但是如果你是一个有经验的开发者你会对这段代码思考：所有的代码都放在同一个文件中，对于一个只有几十行的小应用不存在什么问题，但是如果你增加越来越多的功能时，问题就会出现，所有的代码杂糅在一起代码总量会变得非常大，极其不利于扩展以及维护。我们是否能够采取一定的方式将这段代码拆分开，于是引出来我们的主题-MVC设计模式。

2.什么叫MVC

MVC-Model,View,Controller

Model-模型，在一个应用中，它代表所要操作的所有数据，在前面的小应用中，条目即属于模型。

View-视图，用于展示数据，是一个程序操作的界面，在一个web应用中通常表示为html代码，在本例中，list和button都属于view。

Controller-控制器，处理视图上的事件并且反馈到数据上，如本例中，点击添加按钮，可以添加条目。

MVC的本质是对外提供一组触发器，然后执行一些内部操作，最后返回结果。

3.为什么使用MVC

4.本例的一种MVC实现

Event

function Event(sender) {
    this._sender = sender;
    this._listeners = [];
}

Event.prototype = {
    attach: function (listener) {
        this._listeners.push(listener);
    },
    notify: function (args) {
        var index;

        for (index = 0; index < this._listeners.length; index += 1) {
            this._listeners[index](this._sender, args);
        }
    }
};

Model

/**
 * The Model. Model stores items and notifies
 * observers about changes.
 */
function ListModel(items) {
    this._items = items;
    this._selectedIndex = -1;

    this.itemAdded = new Event(this);
    this.itemRemoved = new Event(this);
    this.selectedIndexChanged = new Event(this);
}

ListModel.prototype = {
    getItems: function () {
        return [].concat(this._items);
    },

    addItem: function (item) {
        this._items.push(item);
        this.itemAdded.notify({
            item: item
        });
    },

    removeItemAt: function (index) {
        var item;

        item = this._items[index];
        this._items.splice(index, 1);
        this.itemRemoved.notify({
            item: item
        });
        if (index === this._selectedIndex) {
            this.setSelectedIndex(-1);
        }
    },

    getSelectedIndex: function () {
        return this._selectedIndex;
    },

    setSelectedIndex: function (index) {
        var previousIndex;

        previousIndex = this._selectedIndex;
        this._selectedIndex = index;
        this.selectedIndexChanged.notify({
            previous: previousIndex
        });
    }
};

View

/**
 * The View. View presents the model and provides
 * the UI events. The controller is attached to these
 * events to handle the user interraction.
 */
function ListView(model, elements) {
    this._model = model;
    this._elements = elements;

    this.listModified = new Event(this);
    this.addButtonClicked = new Event(this);
    this.delButtonClicked = new Event(this);

    var _this = this;

    // attach model listeners
    this._model.itemAdded.attach(function () {
        _this.rebuildList();
    });
    this._model.itemRemoved.attach(function () {
        _this.rebuildList();
    });

    // attach listeners to HTML controls
    this._elements.list.change(function (e) {
        _this.listModified.notify({
            index: e.target.selectedIndex
        });
    });
    this._elements.addButton.click(function () {
        _this.addButtonClicked.notify();
    });
    this._elements.delButton.click(function () {
        _this.delButtonClicked.notify();
    });
}

ListView.prototype = {
    show: function () {
        this.rebuildList();
    },

    rebuildList: function () {
        var list, items, key;

        list = this._elements.list;
        list.html('');

        items = this._model.getItems();
        for (key in items) {
            if (items.hasOwnProperty(key)) {
                list.append($('' + items[key] + ''));
            }
        }
        this._model.setSelectedIndex(-1);
    }
};

Controller

/**
 * The Controller. Controller responds to user actions and
 * invokes changes on the model.
 */
function ListController(model, view) {
    this._model = model;
    this._view = view;

    var _this = this;

    this._view.listModified.attach(function (sender, args) {
        _this.updateSelected(args.index);
    });

    this._view.addButtonClicked.attach(function () {
        _this.addItem();
    });

    this._view.delButtonClicked.attach(function () {
        _this.delItem();
    });
}

ListController.prototype = {
    addItem: function () {
        var item = window.prompt('Add item:', '');
        if (item) {
            this._model.addItem(item);
        }
    },

    delItem: function () {
        var index;

        index = this._model.getSelectedIndex();
        if (index !== -1) {
            this._model.removeItemAt(this._model.getSelectedIndex());
        }
    },

    updateSelected: function (index) {
        this._model.setSelectedIndex(index);
    }
};

程序入口application.js

$(function () {
    var model = new ListModel(['PHP', 'JavaScript']),
        view = new ListView(model, {
            'list': $('#list'),
                'addButton': $('#plusBtn'),
                'delButton': $('#minusBtn')
        }),
        controller = new ListController(model, view);

    view.show();
});

html文件

    

        
    
    

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