data-shaper

Data shaper

The data shaper is a utility for shaping data and resolving related objects and data from normalized, relational data. Through shapes the relation between different parts of the response is declared, and a flat, keyed response is created based on the response objects and collections you've declared.

Why?

While normalized datastructures usually is a good idea it does not always translate so good to what you want to present to a client side app or a 3rd party consumer. The problem is in many cases solved creating lots of custom, which is not trivial to maintain.

How?

Through the declaration of shapes and references to related data you have a fairly flexible and very maintainable way of building responses spanning across multiple collections of data.

Installation

npm install --save data-shaper

Basic usage

var dataShaper = require('data-shaper');

// For the sake of this example the fetchData returns some mock data
function fetchData(id, reference, callback) {
    process.nextTick(function() {
        callback(null, { id: 2, name: 'VG' });
    });
}

dataShaper(
    { id: 1, name: 'Kristoffer', companyId: 2 }, // data to shape
    personShape, // the shape to use
    { fetchData: fetchData }, // dataShaper params
    function(err, res) {
        // do stuff with res here
    }
);

The value of res in the callback is:

{
    persons: { '1' : { id: 1, name: 'Kristoffer', employer: { employers: 1 } } },
    employers: { '2' : { id: 2, name: 'VG' } }
}

---

References

References to values on the passed objects themselves is written as a simple string, like name. Values referencing properties on related data use dot notation.

If have a field companyId on the object and want to get the name of the company you can use companyId.name given that name is a property on the company data object.

Fetching data

In order for the data shaper to be able to resolve data you need to name your foreign keys in a way so that you're able to know what to query. The resolver pass the id and reference to the fetchData function you provide to the data-shaper. You will then have to use the reference to determine where the data is to be fetched from, get the data and return it.

Your fetchData function may look like this

var db = require('your-database-adapter');

function fetchData(id, reference, callback) {
    var tableName = reference.replace(/Id$/, '');

    db(tableName).fetch(id, callback);
}

The data fetcher method is memoized within a dataShaper call by default to speed up fetches, but you have the option of disabling this by passing memoize: false in the options object. Note that the memoization is local only – it won't cache anything across separate calls on the dataShaper function. If you want caching across calls you have to implement that yourself in the fetchData function.

Shapes

Shapes look this:

var simpleShape = {
    collectionName: 'persons',
    shape: {
        id: 'id',
        name: 'name',
        employerId: 'companyId'
    }
};

With this shape, all objects passed to the data shaper will be represented with an object looking like this shape, with the values being fetched from the passed objects.

// This data object
{ id: 1, name: 'Kristoffer', city: 'Oslo', companyId: 5 }

// ...results in a response object like this
{ id: 1, name: 'Kristoffer', employerId: 5 }

A more complex shape, including a relation reference looks like this;

var employersShape = {
    collectionName: 'companies',
    shape: {
        id: 'id',
        name: 'name'
    }
};

var personShape = {
    collectionName: 'persons',
    shape: {
        id: 'id',
        name: 'name',
        employer: {
            reference: 'companyId',
            shape: employerShape
        }
    }
};

When shaping a person object using the personShape the fetchData method you provide is used to resolve the data for the company. In the personShape company is declared using an object with a reference and a shape – a fragment.

License

MIT licensed. See LICENSE.