Signals in GObject are used to support a event-driven programming. Signals can be connected to callback handlers. When they are emitted, these handlers are invoked. To add signals to a type, notice following lines of code:
NOTE: PLEASE READ ALL COMMENT CAREFULLY.
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static void fake_base_class_init(FakeBaseClass *klass, gpointer data) { // ... /* signals */ g_signal_new("base-signal-int", FAKE_TYPE_BASE, G_SIGNAL_RUN_LAST, 0, NULL, NULL, g_cclosure_marshal_VOID__INT, G_TYPE_NONE, 1, G_TYPE_INT, NULL); g_signal_new("base-signal-string", FAKE_TYPE_BASE, G_SIGNAL_RUN_LAST, 0, NULL, NULL, g_cclosure_marshal_VOID__STRING, G_TYPE_NONE, 1, G_TYPE_STRING, NULL); // ... } |
Like properties, signals can be inherited too. Use signals like:
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int main() { // ... FakeBase *base = (FakeBase *)g_object_new(FAKE_TYPE_BASE, NULL); FakeDerived *derived = (FakeDerived *)g_object_new(FAKE_TYPE_DERIVED, NULL); /* Test for signals */ /* 1 <-> 1 */ g_signal_connect(base, "base-signal-int", G_CALLBACK(print_int1), NULL); g_signal_connect(base, "base-signal-string", G_CALLBACK(print_string1), NULL); g_signal_emit_by_name(base, "base-signal-int", 12345); g_signal_emit_by_name(base, "base-signal-string", "abcde"); /* 1 <-> 1+ */ g_signal_connect(base, "base-signal-int", G_CALLBACK(print_int2), NULL); g_signal_emit_by_name(base, "base-signal-int", 123456); /* signal inheritance */ g_signal_connect(derived, "base-signal-int", G_CALLBACK(print_int1), NULL); g_signal_connect(derived, "base-signal-string", G_CALLBACK(print_string1), NULL); g_signal_connect(derived, "derived-signal-int", G_CALLBACK(print_int2), NULL); g_signal_connect(derived, "derived-signal-string", G_CALLBACK(print_string2), NULL); g_signal_emit_by_name(derived, "base-signal-int", 1234567); g_signal_emit_by_name(derived, "base-signal-string", "abcdefg"); g_signal_emit_by_name(derived, "derived-signal-int", 1234567); g_signal_emit_by_name(derived, "derived-signal-string", "abcdefg"); // ... } |
The callback functions are defined simply like:
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void print_int1(GObject *sender, int i, gpointer data) { if (FAKE_IS_DERIVED(sender)) { g_print("Invoking print_int1(): derived.i=%d\n", i); } else if (FAKE_IS_BASE(sender)) { g_print("Invoking print_int1(): base.i=%d\n", i); } } void print_int2(GObject *sender, int i, gpointer data) { if (FAKE_IS_DERIVED(sender)) { g_print("Invoking print_int2(): derived.i=%d\n", i); } else if (FAKE_IS_BASE(sender)) { g_print("Invoking print_int2(): base.i=%d\n", i); } } void print_string1(GObject *sender, gchar* str, gpointer data) { if (FAKE_IS_DERIVED(sender)) { g_print("Invoking print_string1(): derived.str=\"%s\"\n", str); } else if (FAKE_IS_BASE(sender)) { g_print("Invoking print_string1(): base.str=\"%s\"\n", str); } } void print_string2(GObject *sender, gchar* str, gpointer data) { if (FAKE_IS_DERIVED(sender)) { g_print("Invoking print_string2(): derived.str=\"%s\"\n", str); } else if (FAKE_IS_BASE(sender)) { g_print("Invoking print_string2(): base.str=\"%s\"\n", str); } } |
All source code is available in my skydrive: http://cid-481cbe104492a3af.office.live.com/browse.aspx/share/dev/TestOO. In the TestGObject-{date}.zip/TestGObject5 folder.