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# QCCompositionRepository

The `QCCompositionRepository` class represents a system-wide centralized repository of built-in and installed Quartz Composer compositions (`/Library/Compositions` and `~/Library/Compositions`). The `QCCompositionRepository` class cannot be subclassed.

```
class QCCompositionRepository
```

## Overview

Compositions in the repository are represented by the [`QCComposition`](/documentation/Quartz/QCComposition) class. You can use the methods of the `QCCompositionRepository` class to fetch all compositions or only those that meet specific criteria.

## Topics

### Getting the Composition Repository

[`shared()`](/documentation/Quartz/QCCompositionRepository/shared())

Returns the shared instance of the composition repository.

### Fetching Compositions

[`composition(withIdentifier:)`](/documentation/Quartz/QCCompositionRepository/composition(withIdentifier:))

Returns the composition that corresponds to the identifier.

[`compositions(withProtocols:andAttributes:)`](/documentation/Quartz/QCCompositionRepository/compositions(withProtocols:andAttributes:))

Returns an array of compositions that match a set of criteria.

[`allCompositions()`](/documentation/Quartz/QCCompositionRepository/allCompositions())

Returns an array that contains all compositions currently in the composition repository.

### Notifications

[`QCCompositionRepositoryDidUpdateNotification`](/documentation/Quartz/QCCompositionRepositoryDidUpdateNotification)

Posted whenever the list of compositions in the composition repository is updated.


---

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