avifors/doc/queries.md

A MDE tool that generates code from a YAML definition of your app domain model.

# Query the model

Your model can quickly become complex. To mitigate it, Avifors allows you to query the model you have defined.

To do this, you can create queries: they are simple Javascript function taking the model as an argument and returning a part of it. For example, let's say we want to be able, given an attribute, to list every event having this attribute. We will define our query this way:

```javascript
avifors.setQuery(
  'entity:with-attr',                                       // The name of the query
  {
    description: 'List the events having given attribute', // A short description of the query
    arguments: ['attrName'],                               // The list of needed arguments for your query
    resolve: ({model}, {attrName}) => model                // The function resolving the query; first arguments is {avifors, model, argv} (argv is computed from substack/minimist); second argument contains your arguments
        .filter(i => i.type === 'entity' && i.arguments.attributes.some(j => j.name === attrName))
        .map(i => i.arguments.name)                        // Here we only want names of the entities
  }
)
```

We can then use our query using the `query` command:

```
avifors query entity:with-attr user_id
```

This will print something like the following:

```yaml
- name: user_registered
  attributes:
    - user_id
    - email_address
    - password

- name: password_changed
  attributes:
    - user_id
    - new_password
```

Next: [Print generators interfaces](https://github.com/antarestupin/Avifors/tree/master/doc/interface.md)