Adding transformers

New transformers can be added in src/common/transformers

// src/common/transformers/COLUMN.js
const transformation = (context, args) => {
    const sourceField = args.find(a => a.name === 'column');

    if (!sourceField) {
        throw new Error('Invalid Argument for COLUMN transformation');
    }

    return doc => new Promise((resolve, reject) => {
        try {
            if (!doc) {
                resolve(null);
                return;
            }
            resolve(doc[sourceField.value]);
        } catch (error) {
            reject(error);
        }
    });
};

transformation.getMetas = () => ({
    name: 'COLUMN',
    args: [{
        name: 'column',
        type: 'column',
    }],
});

export default transformation;

A transformer can be divided in two parts a transformation function, and a getMetas method.

transformation

The transformation function take a context and an array of arguments.

Context

The context differ based on the environment. This context allow to know the environment (context.env):

• node: server side during publication
• browser: client side during preview

Based on the env, the context expose different functionality. In node:

• dataset: The dataset model that allow to execute mongo queries on the dataset collection.
• fetchLineBy(field, value): That allow to get a raw dataset line where its field equal value.

In browser:

• token: authentification token of the current session
• fetchLineBy(field, value, token): Same as fetchLineBy but also need the token.

Extending the context

To add method to the context, you need to edit the code in two place.

• clientSide: in src/app/lib/getDocumentTransformer.
• Serverside: in src/api/services/getDocumentTransformer, notice that you have access to ctx object from koa.

arguments

The array of arguments representing the configuration of the transformer given by the user.

getMetas

A function that return a meta object describing the transformer and its arguments.

transformation.getMetas = () => ({
    name: 'COLUMN',
    args: [{
        name: 'column',
        type: 'column',
    }],
});

The meta object have the following keys

• name: the name of the transformer, as displayed on the admin
• args: Array describing each args needed by the transformer.
• name: The name of the arg as displayed in the admin
• type: The type of the arg, either:
  • column: the value is the name of a column in the original dataset
  • string: a string