GI.Gio.Interfaces.Initable

Initable is implemented by objects that can fail during initialization. If an object implements this interface then it must be initialized as the first thing after construction, either via initableInit or asyncInitableInitAsync (the latter is only available if it also implements AsyncInitable).

If the object is not initialized, or initialization returns with an error, then all operations on the object except objectRef and objectUnref are considered to be invalid, and have undefined behaviour. They will often fail with g_critical() or g_warning(), but this must not be relied on.

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 initableInit under the cover, returning Nothing 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.

Since: 2.22

Exported types

newtype Initable

Memory-managed wrapper type.

Constructors

Initable (ManagedPtr Initable)

Instances

Eq Initable

Defined in GI.Gio.Interfaces.Initable

Methods

(==) :: Initable -> Initable -> Bool

(/=) :: Initable -> Initable -> Bool

IsGValue Initable

Convert Initable to and from GValue with toGValue and fromGValue.

Defined in GI.Gio.Interfaces.Initable

Methods

toGValue :: Initable -> IO GValue

fromGValue :: GValue -> IO Initable

ManagedPtrNewtype Initable

Defined in GI.Gio.Interfaces.Initable

Methods

toManagedPtr :: Initable -> ManagedPtr Initable

TypedObject Initable

Defined in GI.Gio.Interfaces.Initable

Methods

glibType :: IO GType

GObject Initable

Defined in GI.Gio.Interfaces.Initable

HasParentTypes Initable

Defined in GI.Gio.Interfaces.Initable

type ParentTypes Initable

Defined in GI.Gio.Interfaces.Initable

type ParentTypes Initable = '[Object]

class (GObject o, IsDescendantOf Initable o) => IsInitable o

Type class for types which can be safely cast to Initable, for instance with toInitable.

Instances

(GObject o, IsDescendantOf Initable o) => IsInitable o

Defined in GI.Gio.Interfaces.Initable

toInitable :: (MonadIO m, IsInitable o) => o -> m Initable

Cast to Initable, for types for which this is known to be safe. For general casts, use castTo.

Methods

Overloaded methods

init

initableInit

Arguments

:: (HasCallStack, MonadIO m, IsInitable a, IsCancellable b)

=> a

initable: a Initable.

-> Maybe b

cancellable: optional Cancellable object, Nothing to ignore.

-> m ()

(Can throw GError)

Initializes the object implementing the interface.

This method is intended for language bindings. If writing in C, g_initable_new() should typically be used instead.

The object must be initialized before any real use after initial construction, either with this function or asyncInitableInitAsync.

Implementations may also support cancellation. If cancellable is not Nothing, then initialization can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error IOErrorEnumCancelled will be returned. If cancellable is not Nothing and the object doesn't support cancellable initialization the error IOErrorEnumNotSupported will be returned.

If the object is not initialized, or initialization returns with an error, then all operations on the object except objectRef and objectUnref are considered to be invalid, and have undefined behaviour. See the [introduction][ginitable] for more details.

Callers should not assume that a class which implements Initable can be initialized multiple times, unless the class explicitly documents itself as supporting this. Generally, a class’ implementation of init() can assume (and assert) that it will only be called once. Previously, this documentation recommended all Initable implementations should be idempotent; that recommendation was relaxed in GLib 2.54.

If a class explicitly supports being initialized multiple times, it is recommended that the method is idempotent: multiple calls with the same arguments should return the same results. Only the first call initializes the object; further calls return the result of the first call.

One reason why a class might need to support idempotent initialization is if it is designed to be used via the singleton pattern, with a ObjectClass.constructor that sometimes returns an existing instance. In this pattern, a caller would expect to be able to call initableInit on the result of g_object_new(), regardless of whether it is in fact a new instance.

Since: 2.22

newv

initableNewv

Arguments

:: (HasCallStack, MonadIO m, IsCancellable a)

=> GType

objectType: a GType supporting Initable.

-> [Parameter]

parameters: the parameters to use to construct the object

-> Maybe a

cancellable: optional Cancellable object, Nothing to ignore.

-> m Object

Returns: a newly allocated Object, or Nothing on error (Can throw GError)

Deprecated: (Since version 2.54)Use g_object_new_with_properties() andinitableInit instead. See Parameter for more information.

Helper function for constructing Initable object. This is similar to objectNewv but also initializes the object and returns Nothing, setting an error on failure.

Since: 2.22