## GTypeModule

GTypeModule — Type loading modules

## Synopsis

    #include <glib-object.h>

    struct      GTypeModule;
    struct      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);

## 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.

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

### struct GTypeModule

    struct GTypeModule {
      gchar *name;
    };

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

### struct GTypeModuleClass

    struct GTypeModuleClass {

      GObjectClass parent_class;

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

    };

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

GObjectClass `parent_class` |
gboolean (*`load`) (GTypeModule *module) | loads the module and registers one or more types using `g_type_module_register_type()`.
void (*`unload`) (GTypeModule *module) | 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

## See Also

GTypePlugin | The abstract type loader interface.
GModule | Portable mechanism for dynamically loaded modules.