# ORM

> Like [mongoose](http://mongoosejs.com/docs/guide.html#methods), RxDB has ORM capabilities which can be used to add specific behavior to documents and collections.

# Object-Data-Relational-Mapping

Like [mongoose](http://mongoosejs.com/docs/guide.html#methods), RxDB has ORM capabilities which can be used to add specific behavior to documents and collections.

## statics

Statics are defined collection-wide and can be called on the collection.

### Add statics to a collection

To add static functions, pass a `statics` object when you create your collection. The object contains functions, mapped to their function names.

```javascript
const heroes = await myDatabase.addCollections({
  heroes: {
    schema: mySchema,
    statics: {
      scream: function(){
          return 'AAAH!!';
      }
    }
  }
});

console.log(heroes.scream());
// 'AAAH!!'
```

You can also use the `this` keyword which resolves to the collection:

```javascript
const heroes = await myDatabase.addCollections({
  heroes: {
    schema: mySchema,
    statics: {
      whoAmI: function(){
          return this.name;
      }
    }
  }
});
console.log(heroes.whoAmI());
// 'heroes'
```

## Instance Methods

Instance methods are defined collection-wide. They can be called on the [RxDocuments](./rx-document.md) of the collection.

### Add instance methods to a collection

```javascript
const heroes = await myDatabase.addCollections({
  heroes: {
    schema: mySchema,
    methods: {
      scream: function(){
        return 'AAAH!!';
      }
    }
  }
});
const doc = await heroes.findOne().exec();
console.log(doc.scream());
// 'AAAH!!'
```

Here you can also use the `this` keyword:

```javascript
const heroes = await myDatabase.addCollections({
  heroes: {
    schema: mySchema,
    methods: {
      whoAmI: function(){
          return 'I am ' + this.name + '!!';
      }
    }
  }
});
await heroes.insert({
  name: 'Skeletor'
});
const doc = await heroes.findOne().exec();
console.log(doc.whoAmI());
// 'I am Skeletor!!'
```

## attachment-methods

Attachment methods are defined collection-wide. They can be called on the [RxAttachments](./rx-attachment.md) of the RxDocuments of the collection.

```javascript
const heroes = await myDatabase.addCollections({
  heroes: {
    schema: mySchema,
    attachments: {
      scream: function(){
          return 'AAAH!!';
      }
    }
  }
});
const doc = await heroes.findOne().exec();
const attachment = await doc.putAttachment({
    id: 'cat.txt',
    data: 'meow I am a kitty',
    type: 'text/plain'
});
console.log(attachment.scream());
// 'AAAH!!'
```