Question

我目前正在创建一个应用程序原型，其中包含一个OpenLayers组件（地图本身）。

我想创建具有其他属性的特殊“功能”。

他们应该继承自 OpenLayers.Feature.Vector ，也就是说，使用带有自定义参数和附加属性的构造函数。

我一直在寻找，但我找不到任何关于如何做的简单例子。

*注意：我的应用程序对象结构不是基于“OpenLayers.Class”类型，因此它们是常见的javascript对象。

所以这是应该从OpenLayers.Feature.Vector继承的类，并且应该返回它的特殊实例，

// Class "SpecialRegion"
function SpecialRegion(bounds, options) {

 /* should return an OpenLayers.Feature.Vector with additional properties (objects) which makes this class different */

}

提前致谢。

Answer 1

如果你想扩展我强烈推荐的OpenLayers.Feature.Vector类，你将不得不使用OpenLayers.Class对象：

SpecialRegion = OpenLayers.Class(OpenLayers.Feature.Vector, {
    customAttribute: 'value',

    /**
     * OpenLayers Constructor
     */
    initialize: function(bounds, options) {
        // Call the super constructor, you will have to define the variables geometry, attributes and style
        OpenLayers.Feature.Vector.prototype.initialize.apply(this, {geometry, attributes, style});
        this.customAttribute = 'new value';
    },

    // Each instance will share this method. It's clean and efficient
    customMethod: function(param) {
        ...
    }
});

实例化

var myVector = new SpecialRegion(bounds, options);
myVector.customMethod(param);
var val = myVector.customAttribute;

如果您只想为单个实例定义特殊方法和/或属性，而无需定义它自己的类：

注意：如果您经常这样做，您的应用程序会变得非常混乱，我会建议上面的解决方案。

function customMethod2 = function(param) {
    ...
};

function SpecialRegion(bounds, options) {
    // Call the constructor, you will have to define the variables geometry, attributes and style
    var vector = new OpenLayers.Feature.Vector(geometry, attributes, style);

    vector.customAttribute = 'new value';

    // Each instance created with SpecialRegion will have their own copy of this method, the code is cleaner but it's memory inefficient
    vector.customMethod = function(param) {
        ...
    };

    // Each instance share the same copy of this method (defined on top), the code is harder to read/maintain but it's more memory efficient
    vector.customMethod2 = customMethod2;

    return vector;
};

实例化

var myVector = SpecialRegion(bounds, options);
// Don't use the keyword 'new' here, SpecialRegion is a function, not a proper class.
myVector.customMethod(param);
myVector.customMethod2(param);
var val = myVector.customAttribute;

创建一个继承自“OpenLayers.Feature.Vector”的JavaScript类

1 个答案: