## EDataFactory

EDataFactory — An abstract base class for a backend-based server

## Synopsis

    #include <libebackend/libebackend.h>

    struct              EDataFactory;
    EBackend *          e_data_factory_ref_backend          (EDataFactory *data_factory,
                                                             const gchar *hash_key,
                                                             ESource *source);
    EBackend *          e_data_factory_ref_initable_backend (EDataFactory *data_factory,
                                                             const gchar *hash_key,
                                                             ESource *source,
                                                             GCancellable *cancellable,
                                                             GError **error);
    EBackendFactory *   e_data_factory_ref_backend_factory  (EDataFactory *data_factory,
                                                             const gchar *hash_key);

## Object Hierarchy

      GObject
       +----EDBusServer
             +----EDataFactory
                   +----ESourceRegistryServer

## Implemented Interfaces

EDataFactory implements EExtensible.

## Signals

      "backend-created"                                : Run Last

## Description

## Details

### struct EDataFactory

    struct EDataFactory;

Contains only private data that should be read and manipulated using the functions below.

Since 3.4

### e_data_factory_ref_backend ()

    EBackend *          e_data_factory_ref_backend          (EDataFactory *data_factory,
                                                             const gchar *hash_key,
                                                             ESource *source);

Returns either a newly-created or existing EBackend for ESource. The returned EBackend is referenced for thread-safety and must be unreferenced with `g_object_unref()` when finished with it.

The `data_factory` retains a weak reference to `backend` so it can return the same instance while `backend` is in use. When the last strong reference to `backend` is dropped, `data_factory` will lose its weak reference and will have to create a new EBackend instance the next time the same `hash_key` and `source` are requested.

If no suitable EBackendFactory exists, the function returns `NULL`.

`data_factory` : | an EDataFactory
`hash_key` : | hash key for an EBackendFactory
`source` : | an ESource
Returns : | an EBackend for `source`, or `NULL`

Since 3.6

### e_data_factory_ref_initable_backend ()

    EBackend *          e_data_factory_ref_initable_backend (EDataFactory *data_factory,
                                                             const gchar *hash_key,
                                                             ESource *source,
                                                             GCancellable *cancellable,
                                                             GError **error);

Similar to `e_data_factory_ref_backend()`, but allows for backends that implement the GInitable interface so they can fail gracefully if they are unable to initialize critical resources, such as a cache database.

Returns either a newly-created or existing EBackend for ESource. The returned EBackend is referenced for thread-safety and must be unreferenced with `g_object_unref()` when finished with it.

If the newly-created backend implements the GInitable interface, then `g_initable_init()` is also called on it using `cancellable` and `error`.

The `data_factory` retains a weak reference to `backend` so it can return the same instance while `backend` is in use. When the last strong reference to `backend` is dropped, `data_factory` will lose its weak reference and will have to create a new EBackend instance the next time the same `hash_key` and `source` are requested.

If no suitable EBackendFactory exists, or if the EBackend fails to initialize, the function sets `error` and returns `NULL`.

`data_factory` : | an EDataFactory
`hash_key` : | hash key for an EBackendFactory
`source` : | an ESource
`cancellable` : | optional GCancellable object, or `NULL`
`error` : | return location for a GError, or `NULL`
Returns : | an EBackend for `source`, or `NULL`

Since 3.8

### e_data_factory_ref_backend_factory ()

    EBackendFactory *   e_data_factory_ref_backend_factory  (EDataFactory *data_factory,
                                                             const gchar *hash_key);

Returns the EBackendFactory for `hash_key`, or `NULL` if no such factory is registered.

The returned EBackendFactory is referenced for thread-safety. Unreference the EBackendFactory with `g_object_unref()` when finished with it.

`data_factory` : | an EDataFactory
`hash_key` : | hash key for an EBackendFactory
Returns : | the EBackendFactory for `hash_key`, or `NULL`

Since 3.6

## Signal Details

### The `"backend-created"` signal

    void                user_function                      (EDataFactory *data_factory,
                                                            EBackend     *backend,
                                                            gpointer      user_data)         : Run Last

Emitted when a new EBackend is instantiated by way of `e_data_factory_ref_backend()`. Extensions can connect to this signal to perform additional initialization on the EBackend.

`data_factory` : | the EDataFactory which emitted the signal
`backend` : | the newly-created EBackend
`user_data` : | user data set when the signal handler was connected.

Since 3.8