javascript - How can I add an instance method to all Models in sails.js? - Stack Overflow

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I'd like to add a default toDisplay function to all models which will use metadata, not unlike attribute/association definitions, to perform manipulations on the instance's attributes/associations making them suitable for display in the UI.

for example:

Foo.findOne(someId)
  .exec(function(err, foo) {
    ...
    res.view({
      foo: foo.toDisplay(),
    });
  });

I'd like to add a default toDisplay function to all models which will use metadata, not unlike attribute/association definitions, to perform manipulations on the instance's attributes/associations making them suitable for display in the UI.

for example:

Foo.findOne(someId)
  .exec(function(err, foo) {
    ...
    res.view({
      foo: foo.toDisplay(),
    });
  });

So, I'd like to add this function too all models. I can imagine a

Model.prototype.toDisplay = ... 

solution, but I'm not sure where to get Model from (some long require('waterline/..../model') path?), and if I had Model, where to put that snip-it.

Please advise.

• javascript
• node.js
• express
• sails.js
• waterline

Share Improve this question Follow edited Apr 23, 2015 at 23:33 Travis Webb 15k99 gold badges5757 silver badges110110 bronze badges asked Dec 18, 2014 at 3:08 umassthrowerumassthrower 1,39711 gold badge1111 silver badges1515 bronze badges 1

• OK, let's see if adding more tags gets this more than 12 views in 40 hours (4 of which are mine). – umassthrower Commented Dec 19, 2014 at 14:56

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 10

Model configuration is fully documented here on SailsJS. @umassthrower is correct in pointing out that adding an instance method to config/models.js would add it to all of your models; he's also correct in observing that this is not the intended use of the config file.

The reason you're finding this a bit more challenging in Sails than Rails is that Ruby has real classes and inheritance, and Javascript just has objects. One fairly clean way to simulate inheritance and extend your model objects from a "base" object would be to use something like Lodash's _.merge function. For example you could save your base model in lib/BaseModel.js:

// lib/BaseModel.js
module.exports = {

  attributes: {

    someAttribute: 'string',

    someInstanceFunction: function() {
      // do some amazing (synchronous) calculation here
    }

  }

};

Then in your model file, require lodash and use _.extend:

// api/models/MyModel.js
var _ = require('lodash');
var BaseModel = require("../../lib/BaseModel.js");
module.exports = _.merge({}, BaseModel, {

  attributes: {

    someOtherAttribute: 'integer'

  }

};

The attributes from your base model will be merged with MyModel, with MyModel taking precedence.

Setting the first argument to the empty model {} is important here; _.merge is destructive for the first object sent in, so if you just did _.merge(BaseModel, {...} then the base model would be modified.

Also, remember to npm install lodash!

In Sails 0.x, when the moduleloader was loaded, you could access to sails.models directly, but now in 1.x this is not ready yet, so, my solution to this was creating a custom hook that wraps the loadModels function of sails.modules, this may not be the best solution but works for me @adam-pietrasiak hope this works for you too :) I am also super lazy when it es to repeating code.

// provide this code in api/hooks/overrides.js or use another name, who cares

  
const _ = require('lodash');

module.exports = function (sails) {
    return {
        defaults: {},
        savedModelLoad: null,

        configure: function () {
            this.savedModelLoad = this.savedModelLoad || sails.modules.loadModels;
            sails.modules.loadModels = this.loadModelsAndApplyOverrides;
        },

        loadModelsAndApplyOverrides: function(cb){
            this.savedModelLoad(function (err, models) {
                const newModels = _.map(models, applyModelOverrides);

                cb(err, newModels);
            });
        }
    };
};

function applyModelOverrides(model) {
    return _.merge(model, {
      // do your custom stuff here
        attributes: {

            someAttribute: 'string',

            someInstanceFunction: function() {
                // do some amazing (synchronous) calculation here
            }

        }
    });
}

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