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dynamic key in JSON file (used by backbone.js models for example…)



I am trying to create a backbone.js model with dynamic keys but can't seem to get it done right.





Here's my model:







window.MyModel = Backbone.Model.extend({

myDynamicVar : "country",

urlRoot: "api/myModel",

defaults: {

"id": null,

this.myDynamicVar : "USA",

"country": {

"route":"test/test/test",

"class":".usa2",

"txt":"USA 2"

},

"region": "California",

"year": "",

"description": "",

"picture": ""

}

});







Here I am trying to have myDynamicVar replaced by its content in my model. Any thought how I could get this done? Thanks in advance, Jimmy


Comments

  1. You cannot use a variable in defining the object key. You can try something like this.

    window.MyModel = Backbone.Model.extend({
    myDynamicVar : "country",
    urlRoot: "api/myModel",
    defaults: {
    "id": null,
    "country": {
    "route":"test/test/test",
    "class":".usa2",
    "txt":"USA 2"
    },
    "region": "California",
    "year": "",
    "description": "",
    "picture": ""
    }
    });

    window.MyModel.defaults[this.myDynamicVar] = "USA";

    ReplyDelete
  2. You won't be able to do that directly; the left side of the ":" in an object literal must be a constant. What you can do is this:

    window.MyModel = Backbone.Model.extend({
    myDynamicVar : "country",
    urlRoot: "api/myModel",
    defaults: function(fieldName) {
    var value = {
    "id": null,
    "country": {
    "route":"test/test/test",
    "class":".usa2",
    "txt":"USA 2"
    },
    "region": "California",
    "year": "",
    "description": "",
    "picture": ""
    };
    value[fieldName] = "USA";
    return value;
    }(this.myDynamicVar)
    });


    edit — ah, I just noticed that "myDynamicVar" itself is part of the outer object. There's no way to refer to it with this in such a way, so if that's what you're trying to do the code would be different:

    window.MyModel = Backbone.Model.extend(function() {
    var value = {
    myDynamicVar : "country",
    urlRoot: "api/myModel",
    defaults: {
    "id": null,
    "country": {
    "route":"test/test/test",
    "class":".usa2",
    "txt":"USA 2"
    },
    "region": "California",
    "year": "",
    "description": "",
    "picture": ""
    }
    };

    value.defaults.[value.myDynamicVar] = "USA";
    return value;
    }());


    If you want myDynamicVar itself to be dynamic, then you could pass it in as a parameter:

    window.MyModel = Backbone.Model.extend(function(whichProperty) {
    var value = {
    myDynamicVar : "country",
    urlRoot: "api/myModel",
    defaults: {
    "id": null,
    "country": {
    "route":"test/test/test",
    "class":".usa2",
    "txt":"USA 2"
    },
    "region": "California",
    "year": "",
    "description": "",
    "picture": ""
    }
    };

    value.defaults.[value[whichProperty]] = "USA";
    return value;
    }("myDynamicVar"));

    ReplyDelete

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