owl/doc/reference/environment.md

🦉 Environment 🦉

Content

• Overview
• Setting an Environment
• Content of an Environment

Overview

An environment is an object which contains a QWeb instance. Whenever a root component is created, it is assigned an environment (see below for more info on this). This environment is then automatically given to each sub component (and accessible in the this.env property).

    Root
    /  \
   A    B

This way, all components share the same QWeb instance. Owl internally requires that the environment has a qweb key which maps to a QWeb instance. This is the QWeb instance that will be used to render each templates in this specific component tree. Note that if no QWeb instance is provided, Owl will simply generate it on the fly.

The environment is mostly static. Each application is free to add anything to the environment, which is very useful, since this can be accessed by each sub component.

Setting an environment

An Owl application needs an environment to be executed. The environment has an important key: the QWeb instance, which will render all templates.

Whenever a root component App is mounted, Owl will setup a valid environment by following the next steps:

• take the env object defined on App.env (if no env was explicitely setup, this will be return the empty env object defined on Component)
• if env.qweb is not set, then Owl will create a QWeb instance.

The correct way to customize an environment is to simply set it up on the root component class, before the first component is created:

App.env = {
    _t: myTranslateFunction,
    user: {...},
    services: {
        ...
    },
};
const app = new App();
app.mount(document.body);

It is also possible to simply share an environment between all root components, by simply doing this:

Component.env = myEnv; // will be the default env for all components

Content of an Environment

Some good use cases for additional keys in the environment are:

• some configuration keys,
• session information,
• generic services (such as doing rpcs, or accessing local storage).

Doing it this way means that components are easily testable: we can simply create a test environment with mock services.

For example:

async function myEnv() {
  const templates = await loadTemplates();
  const qweb = new QWeb({ templates });
  const session = getSession();

  return {
    _t: myTranslateFunction,
    session: session,
    qweb: qweb,
    services: {
      localStorage: localStorage,
      rpc: rpc
    },
    debug: false,
    inMobileMode: true
  };
}

async function start() {
  App.env = await myEnv();
  const app = new App();
  await app.mount(document.body);
}