GInitable

GInitable — Failable object initialization interface

Synopsis

#include <gio/gio.h>

                    GInitable;
struct              GInitableIface;
gboolean            g_initable_init                     (GInitable *initable,
                                                         GCancellable *cancellable,
                                                         GError **error);
gpointer            g_initable_new                      (GType object_type,
                                                         GCancellable *cancellable,
                                                         GError **error,
                                                         const gchar *first_property_name,
                                                         ...);
GObject *           g_initable_new_valist               (GType object_type,
                                                         const gchar *first_property_name,
                                                         va_list var_args,
                                                         GCancellable *cancellable,
                                                         GError **error);
gpointer            g_initable_newv                     (GType object_type,
                                                         guint n_parameters,
                                                         GParameter *parameters,
                                                         GCancellable *cancellable,
                                                         GError **error);

Object Hierarchy

  GInterface
   +----GInitable

Prerequisites

GInitable requires GObject.

Known Implementations

GInitable is implemented by GCharsetConverter, GDBusConnection, GDBusProxy, GDBusServer and GSocket.

Description

GInitable is implemented by objects that can fail during initialization. If an object implements this interface the g_initable_init() function must be called as the first thing after construction. If g_initable_init() is not called, or if it returns an error, all further operations on the object should fail, generally with a G_IO_ERROR_NOT_INITIALIZED error.

Users of objects implementing this are not intended to use the interface method directly, instead it will be used automatically in various ways. For C applications you generally just call g_initable_new() directly, or indirectly via a foo_thing_new() wrapper. This will call g_initable_init() under the cover, returning NULL and setting a GError on failure (at which point the instance is unreferenced).

For bindings in languages where the native constructor supports exceptions the binding could check for objects implemention GInitable during normal construction and automatically initialize them, throwing an exception on failure.

Details

GInitable

typedef struct _GInitable GInitable;

Interface for initializable objects.

Since 2.22

struct GInitableIface

struct GInitableIface {
  GTypeInterface g_iface;

  /* Virtual Table */

  gboolean    (* init) (GInitable    *initable,
			GCancellable *cancellable,
			GError      **error);
};

Provides an interface for initializing object such that initialization may fail.

GTypeInterface g_iface;

 The parent interface.

init ()

 Initializes the object.

Since 2.22

g_initable_init ()

gboolean            g_initable_init                     (GInitable *initable,
                                                         GCancellable *cancellable,
                                                         GError **error);

Initializes the object implementing the interface. This must be done before any real use of the object after initial construction.

Implementations may also support cancellation. If cancellable is not NULL, then initialization can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned. If cancellable is not NULL and the object doesn't support cancellable initialization the error G_IO_ERROR_NOT_SUPPORTED will be returned.

If this function is not called, or returns with an error then all operations on the object should fail, generally returning the error G_IO_ERROR_NOT_INITIALIZED.

Implementations of this method must be idempotent, i.e. multiple calls to this function with the same argument should return the same results. Only the first call initializes the object, further calls return the result of the first call. This is so that its safe to implement the singleton pattern in the GObject constructor function.

initable :

 a GInitable.

cancellable :

 optional GCancellable object, NULL to ignore.

error :

 a GError location to store the error occuring, or NULL to ignore.

Returns :

 TRUE if successful. If an error has occurred, this function will return FALSE and set error appropriately if present.

Since 2.22

g_initable_new ()

gpointer            g_initable_new                      (GType object_type,
                                                         GCancellable *cancellable,
                                                         GError **error,
                                                         const gchar *first_property_name,
                                                         ...);

Helper function for constructing GInitiable object. This is similar to g_object_new() but also initializes the object and returns NULL, setting an error on failure.

object_type :

 a GType supporting GInitable.

cancellable :

 optional GCancellable object, NULL to ignore.

error :

 a GError location to store the error occuring, or NULL to ignore.

first_property_name :

 the name of the first property, or NULL if no properties

... :

 the value if the first property, followed by and other property value pairs, and ended by NULL.

Returns :

 a newly allocated GObject, or NULL on error. [transfer full]

Since 2.22

g_initable_new_valist ()

GObject *           g_initable_new_valist               (GType object_type,
                                                         const gchar *first_property_name,
                                                         va_list var_args,
                                                         GCancellable *cancellable,
                                                         GError **error);

Helper function for constructing GInitiable object. This is similar to g_object_new_valist() but also initializes the object and returns NULL, setting an error on failure.

object_type :

 a GType supporting GInitable.

first_property_name :

 the name of the first property, followed by the value, and other property value pairs, and ended by NULL.

var_args :

 The var args list generated from first_property_name.

cancellable :

 optional GCancellable object, NULL to ignore.

error :

 a GError location to store the error occuring, or NULL to ignore.

Returns :

 a newly allocated GObject, or NULL on error. [transfer full]

Since 2.22

g_initable_newv ()

gpointer            g_initable_newv                     (GType object_type,
                                                         guint n_parameters,
                                                         GParameter *parameters,
                                                         GCancellable *cancellable,
                                                         GError **error);

Helper function for constructing GInitiable object. This is similar to g_object_newv() but also initializes the object and returns NULL, setting an error on failure.

object_type :

 a GType supporting GInitable.

n_parameters :

 the number of parameters in parameters

parameters :

 the parameters to use to construct the object

cancellable :

 optional GCancellable object, NULL to ignore.

error :

 a GError location to store the error occuring, or NULL to ignore.

Returns :

 a newly allocated GObject, or NULL on error. [transfer full]

Since 2.22

See Also

GAsyncInitable
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