Compares the user data for the key key on object with oldval, and if they are the same, replaces oldval with newval.

This is like a typical atomic compare-and-exchange operation, for user data on an object.

If the previous value was replaced then ownership of the old value (oldval) is passed to the caller, including the registered destroy notify for it (passed out in old_destroy). It’s up to the caller to free this as needed, which may or may not include using old_destroy as sometimes replacement should not destroy the object in the normal way.

See g_object_set_data() for guidance on using a small, bounded set of values for key.

class ObjectG


key string

a string, naming the user data pointer

oldval void*

the old value to compare against

newval void*

the new value

destroy GDestroyNotify

a destroy notify for the new value

oldDestroy GDestroyNotify

destroy notify for the existing value

Return Value

Type: bool

TRUE if the existing value for key was replaced by newval, FALSE otherwise.