Override method of an existing instance

Question

I'm trying to extend an existing Durandal router plugin instance already created with the help of RequireJS.

The method map() should be overriden to add extra mapping parameters.

How should I access the original method from the modified one?

index.js

define([ 'durandal/app', 'app/childRouter'], function(
        app, childRouter) {
    childRouter.map([ {
        route : 'details/:id',
        moduleId : 'details/index',
    }, {
        route : 'details/tabs/base',
        moduleId : 'details/tabs/base',
    } ]);
    childRouter.buildNavigationModel();

    return {
        router : childRouter
    };
});

childRouter.js

define([ 'durandal/app', 'plugins/router'], function(
        app, router) {

    var childRouter = router.createChildRouter();
    childRouter._map = childRouter.map;
    childRouter.map = function(data) {
        data.unshift({
            route : [ '', 'grid' ],
            moduleId : 'grid/index',
        });
        childRouter._map(data);//CALLS THE OVERRIDEN METHOD AGAIN INSTEAD OF ORIGINAL
    };
    return childRouter;
});

score 1 · Answer 1 · answered Feb 11 '16 at 17:49

1

If you want to still call the original "map" function, you'll need to store it before you overwrite it. It's a bit "hacky" to replace functions in this way, but if you REALLY had to do it, this will work:

var childRouter = router.createChildRouter();
childRouter.originalMap = childRouter.map;  // Save original
    childRouter.map = function(data) {
        data.unshift({
            route : [ '', 'grid' ],
            moduleId : 'grid/index',
        });
        childRouter.originalMap(data);    // Call original
    };

answered Feb 11 '16 at 17:49

jestermax

21
1
2

Tried it, but instead of calling the original `map()` it calls the overriden one again. I don't understand what's going on? – Peter G. Feb 12 '16 at 09:32
I need a small clarification: are you intending on calling the original map function inside of the overridden one? or do you want it callable just in general? – jestermax Feb 12 '16 at 13:14
Yes exactly, it should be callable inside the overriden one. I found it works outside Durandal (for example when you create JSFiddle), but not inside. I tried debugging the sequence of in which the functions get called and found nothing unusual. I wonder why the function calls itself again instead of the stored original. – Peter G. Feb 12 '16 at 16:10

Override method of an existing instance

1 Answers1