GTypeModule
3
GOBJECT Library

# GTypeModule

Type loading modules

## Synopsis

    #include <glib-object.h>

                        GTypeModule;
                        GTypeModuleClass;
    gboolean            g_type_module_use                   (GTypeModule *module);
    void                g_type_module_unuse                 (GTypeModule *module);
    void                g_type_module_set_name              (GTypeModule *module,
                                                             const gchar *name);
    GType               g_type_module_register_type         (GTypeModule *module,
                                                             GType parent_type,
                                                             const gchar *type_name,
                                                             const GTypeInfo *type_info,
                                                             GTypeFlags flags);
    void                g_type_module_add_interface         (GTypeModule *module,
                                                             GType instance_type,
                                                             GType interface_type,
                                                             const GInterfaceInfo *interface_info);
    GType               g_type_module_register_enum         (GTypeModule *module,
                                                             const gchar *name,
                                                             const GEnumValue *const _static_values);
    GType               g_type_module_register_flags        (GTypeModule *module,
                                                             const gchar *name,
                                                             const GFlagsValue *const _static_values);

## Object Hierarchy

      GObject
       +----GTypeModule

## Implemented Interfaces

GTypeModule implements GTypePlugin.

## Description

GTypeModule provides a simple implementation of the GTypePlugin interface. The model of GTypeModule is a dynamically loaded module which implements some number of types and interface implementations. When the module is loaded, it registers its types and interfaces using `g_type_module_register_type()` and `g_type_module_add_interface()`. As long as any instances of these types and interface implementations are in use, the module is kept loaded. When the types and interfaces are gone, the module may be unloaded. If the types and interfaces become used again, the module will be reloaded. Note that the last unref can not happen in module code, since that would lead to the caller's code being unloaded before `g_object_unref()` returns to it.

Keeping track of whether the module should be loaded or not is done by using a use count - it starts at zero, and whenever it is greater than zero, the module is loaded. The use count is maintained internally by the type system, but also can be explicitly controlled by `g_type_module_use()` and `g_type_module_unuse()`. Typically, when loading a module for the first type, `g_type_module_use()` will be used to load it so that it can initialize its types. At some later point, when the module no longer needs to be loaded except for the type implementations it contains, `g_type_module_unuse()` is called.

GTypeModule does not actually provide any implementation of module loading and unloading. To create a particular module type you must derive from GTypeModule and implement the load and unload functions in GTypeModuleClass.

## Details

### GTypeModule

    typedef struct {
      gchar *name;
    } GTypeModule;

The members of the GTypeModule structure should not be accessed directly, except for the `name` field.

gchar *name;

  the name of the module

### GTypeModuleClass

    typedef struct {
      GObjectClass parent_class;

      gboolean (* load)   (GTypeModule *module);
      void     (* unload) (GTypeModule *module);
    } GTypeModuleClass;

In order to implement dynamic loading of types based on GTypeModule, the `load` and `unload` functions in GTypeModuleClass must be implemented.

GObjectClass parent_class;

  the parent class

load ()

  loads the module and registers one or more types using `g_type_module_register_type()`.

unload ()

  unloads the module

### g_type_module_use ()

    gboolean            g_type_module_use                   (GTypeModule *module);

Increases the use count of a GTypeModule by one. If the use count was zero before, the plugin will be loaded.

`module` :

  a GTypeModule

Returns :

  `FALSE` if the plugin needed to be loaded and loading the plugin failed.

### g_type_module_unuse ()

    void                g_type_module_unuse                 (GTypeModule *module);

Decreases the use count of a GTypeModule by one. If the result is zero, the module will be unloaded. (However, the GTypeModule will not be freed, and types associated with the GTypeModule are not unregistered. Once a GTypeModule is initialized, it must exist forever.)

`module` :

  a GTypeModule

### g_type_module_set_name ()

    void                g_type_module_set_name              (GTypeModule *module,
                                                             const gchar *name);

Sets the name for a GTypeModule

`module` :

  a GTypeModule.

`name` :

  a human-readable name to use in error messages.

### g_type_module_register_type ()

    GType               g_type_module_register_type         (GTypeModule *module,
                                                             GType parent_type,
                                                             const gchar *type_name,
                                                             const GTypeInfo *type_info,
                                                             GTypeFlags flags);

Looks up or registers a type that is implemented with a particular type plugin. If a type with name `type_name` was previously registered, the GType identifier for the type is returned, otherwise the type is newly registered, and the resulting GType identifier returned.

When reregistering a type (typically because a module is unloaded then reloaded, and reinitialized), `module` and `parent_type` must be the same as they were previously.

As long as any instances of the type exist, the type plugin will not be unloaded.

`module` :

  a GTypeModule

`parent_type` :

  the type for the parent class

`type_name` :

  name for the type

`type_info` :

  type information structure

`flags` :

  flags field providing details about the type

Returns :

  the new or existing type ID

### g_type_module_add_interface ()

    void                g_type_module_add_interface         (GTypeModule *module,
                                                             GType instance_type,
                                                             GType interface_type,
                                                             const GInterfaceInfo *interface_info);

Registers an additional interface for a type, whose interface lives in the given type plugin. If the interface was already registered for the type in this plugin, nothing will be done.

As long as any instances of the type exist, the type plugin will not be unloaded.

`module` :

  a GTypeModule

`instance_type` :

  type to which to add the interface.

`interface_type` :

  interface type to add

`interface_info` :

  type information structure

### g_type_module_register_enum ()

    GType               g_type_module_register_enum         (GTypeModule *module,
                                                             const gchar *name,
                                                             const GEnumValue *const _static_values);

Looks up or registers an enumeration that is implemented with a particular type plugin. If a type with name `type_name` was previously registered, the GType identifier for the type is returned, otherwise the type is newly registered, and the resulting GType identifier returned.

As long as any instances of the type exist, the type plugin will not be unloaded.

`module` :

  a GTypeModule

`name` :

  name for the type

`_static_values` :

Returns :

  the new or existing type ID

Since 2.6

### g_type_module_register_flags ()

    GType               g_type_module_register_flags        (GTypeModule *module,
                                                             const gchar *name,
                                                             const GFlagsValue *const _static_values);

Looks up or registers a flags type that is implemented with a particular type plugin. If a type with name `type_name` was previously registered, the GType identifier for the type is returned, otherwise the type is newly registered, and the resulting GType identifier returned.

As long as any instances of the type exist, the type plugin will not be unloaded.

`module` :

  a GTypeModule

`name` :

  name for the type

`_static_values` :

Returns :

  the new or existing type ID

Since 2.6

## See Also

GTypePlugin

  The abstract type loader interface.

GModule

  Portable mechanism for dynamically loaded modules.