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docs: Add vfunc NULL checks to GObject how-to examples

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Not setting a pure vfunc is a programmer error, so can be handled with a
g_return_if_fail() rather than needing a g_warning().

https://bugzilla.gnome.org/show_bug.cgi?id=744060
This commit is contained in:
Philip Withnall 2015-02-20 13:14:08 +00:00
parent 82abb80553
commit a76242b35a
1 changed files with 28 additions and 14 deletions
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42
docs/reference/gobject/tut_howto.xml
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@ -571,9 +571,14 @@ void maman_bar_do_action (MamanBar *self, /* parameters */);
void
maman_bar_do_action (MamanBar *self, /* parameters */)
{
MamanBarClass *klass;
g_return_if_fail (MAMAN_IS_BAR (self));
MAMAN_BAR_GET_CLASS (self)->do_action (self, /* parameters */);
klass = MAMAN_BAR_GET_CLASS (self);
g_return_if_fail (klass->do_action != NULL);
klass->do_action (self, /* parameters */);
}
</programlisting></informalexample>
The code above simply redirects the <function>do_action</function> call
@ -596,7 +601,7 @@ maman_bar_real_do_action_two (MamanBar *self, /* parameters */)
}
static void
maman_bar_class_init (BarClass *klass)
maman_bar_class_init (MamanBarClass *klass)
{
/* this is not necessary, except for demonstration purposes.
*
@ -611,27 +616,31 @@ maman_bar_class_init (BarClass *klass)
void
maman_bar_do_action_one (MamanBar *self, /* parameters */)
{
MamanBarClass *klass;
g_return_if_fail (MAMAN_IS_BAR (self));
klass = MAMAN_BAR_GET_CLASS (self);
/* if the method is purely virtual, then it is a good idea to
* check that it has been overridden before calling it, and,
* depending on the intent of the class, either ignore it silently
* or warn the user.
/
if (MAMAN_BAR_GET_CLASS (self)->do_action_one != NULL)
MAMAN_BAR_GET_CLASS (self)->do_action_one (self, /* parameters */);
else
g_warning ("Class '%s' does not override the mandatory "
"MamanBarClass.do_action_one() virtual function.",
G_OBJECT_TYPE_NAME (self));
*/
g_return_if_fail (klass->do_action != NULL);
klass->do_action_one (self, /* parameters */);
}
void
maman_bar_do_action_two (MamanBar *self, /* parameters */)
{
MamanBarClass *klass;
g_return_if_fail (MAMAN_IS_BAR (self));
MAMAN_BAR_GET_CLASS (self)->do_action_two (self, /* parameters */);
klass = MAMAN_BAR_GET_CLASS (self);
if (klass->do_action_two != NULL)
klass->do_action_two (self, /* parameters */);
}
</programlisting></informalexample>
</para>
@ -653,6 +662,10 @@ struct _MamanBarClass
/* stuff */
void (* helper_do_specific_action) (MamanBar *self, /* parameters */);
/* Padding to allow adding up to 12 new virtual functions without
* breaking ABI. */
gpointer padding[12];
};
void maman_bar_do_any_action (MamanBar *self, /* parameters */);
@ -670,6 +683,8 @@ maman_bar_do_specific_action (MamanBar *self, /* parameters */)
void
maman_bar_do_any_action (MamanBar *self, /* parameters */)
{
g_return_if_fail (MAMAN_IS_BAR (self));
/* random code here */
/*
@ -965,8 +980,7 @@ maman_ibaz_interface_init (MamanIbazInterface *iface)
static void
maman_baz_init (MamanBaz *self)
{
MamanBaz *self = MAMAN_BAZ (instance);
self->instance_member = 0xdeadbeaf;
self->instance_member = 0xdeadbeef;
}
</programlisting></informalexample>
</para>
@ -1043,7 +1057,7 @@ maman_ibaz_interface_init (MamanIbazInterface *iface)
static void
maman_bar_class_init (MamanBarClass *klass)
{
/* Nothing here. */
}
static void
@ -1118,7 +1132,6 @@ maman_ibaz_default_init (MamanIbazInterface *iface)
The following code snippet shows the modifications needed in the
<type>MamanBaz</type> declaration and implementation above:
<informalexample><programlisting>
struct _MamanBaz
{
GObject parent_instance;
@ -1210,6 +1223,7 @@ static void
maman_derived_ibaz_do_action (MamanIbaz *ibaz)
{
MamanDerivedBaz *self = MAMAN_DERIVED_BAZ (ibaz);
g_print ("DerivedBaz implementation of Ibaz interface Action\n");
}