How can I create a new function inside a existent class in OpenLayers?

Question

I want to add some functions inside a existent class in OpenLayers. For example, I want to add function A() and B() and a variable C inside OpenLayers.Layer.Vector.

var X = function() {
    A() = funtion { /* something */ },

    B() = funtion { /* something */ },

    C = 'something'

}

So when I create a new layer inside a map object I could call those function by:

map.layer[1].A();

or could change:

map.layer[1].C = 'something else';

I tried many ways but didn't worked well. And most of the time, when I tried to change the C var inside one layer it changed the other too.

Answer 1

You have two options:

1. add a method or property to an instance (this vector layer object only)
2. add a method or property to the vector prototype (all vector layers, even already existing ones)

Option 1:

map.layer[1].A = function() {

};
map.layer[1].B = function() {
    
};
map.layer[1].C = 'something';

//later...

map.layer[1].A();
map.layer[1].B();
map.layer[1].C = 'something else';

OR:

var X = function() {
    A() = funtion { /* something */ },

    B() = funtion { /* something */ },

    C = 'something'
};
map.layer[1].myX = X; //<-- Augment OpenLayers Vector Class with X.

map.layer[1].myX.A();

map.layer[1].myX.B();

map.layer[1].myX.C = "Something Else";

Option 2:

You could augment it's prototype like so:

OpenLayers.Layer.Vector.prototype.A = function () {
    alert(this.CLASS_NAME);
};
map.layer[1].A();

One was is NOT better than the Other. It just depends on what you want to do.

Answer 2

Look at applyDefaults where you would define a 'from' object:

var from = {
    A: function() {},
    B: function() {},
    C: "hello"
};

var layer1 = OpenLayers.Util.applyDefaults(map.layer[1], from);

This should give you a unique A,B,C value on each to object. It's probably not what you really want to do. You probably really want C to be unique and use a single instance of A and B. If that's the case look into OpenLayers.Util.extend for A and B and then simply set to.C = "value".