1 files changed, 101 insertions, 0 deletions
diff --git a/nerv/examples/oop_example.c b/nerv/examples/oop_example.c
new file mode 100644
index 0000000..59dfc5a
--- /dev/null
+++ b/nerv/examples/oop_example.c
@@ -0,0 +1,101 @@
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "../common.h"
+
+#define SQR(x) ((x) * (x))
+
+const char *point_tname = "nerv.Point";
+const char *better_point_tname = "nerv.BetterPoint";
+
+typedef struct {
+    double x, y;
+} Point;
+
+static int point_norm (lua_State *L) {
+    Point *p = luaT_checkudata(L, 1, point_tname);
+    lua_pushnumber(L, sqrt(SQR(p->x) + SQR(p->y)));
+    return 1;
+}
+
+static int point_set_x (lua_State *L) {
+    Point *p = luaT_checkudata(L, 1, point_tname);
+    p->x = luaL_checknumber(L, 2);
+    return 0;
+}
+
+static int point_set_y (lua_State *L) {
+    Point *p = luaT_checkudata(L, 1, point_tname);
+    p->y = luaL_checknumber(L, 2);
+    return 0;
+}
+
+/* generic constructor */
+void point_new_(Point *self, double x, double y) {
+    self->x = x;
+    self->y = y;
+}
+
+int point_new(lua_State *L) {
+    /* `_new` function should create the object itself */
+    Point *self = (Point *)malloc(sizeof(Point));
+    point_new_(self, luaL_checknumber(L, 1), luaL_checknumber(L, 2));
+    luaT_pushudata(L, self, point_tname);
+    fprintf(stderr, "[example] %s constructor is invoked\n",
+            point_tname);
+    return 1;
+}
+
+static const luaL_Reg point_methods[] = {
+    {"set_x", point_set_x},
+    {"set_y", point_set_y},
+    {"norm", point_norm},
+    {NULL, NULL}
+};
+
+
+/* the subclass method overrides the one from baseclass */
+static int better_point_norm (lua_State *L) {
+    Point *p = luaT_checkudata(L, 1, point_tname);
+    lua_pushnumber(L, fabs(p->x) + fabs(p->y));
+    return 1;
+}
+
+int better_point_new(lua_State *L) {
+    /* `_new` function should create the object itself */
+    Point *self = (Point *)malloc(sizeof(Point));
+    point_new_(self, luaL_checknumber(L, 1), luaL_checknumber(L, 2));
+    luaT_pushudata(L, self, better_point_tname);
+    fprintf(stderr, "[example] %s constructor is invoked\n",
+            better_point_tname);
+    return 1;
+}
+
+static const luaL_Reg better_point_methods[] = {
+    {"norm", better_point_norm},
+    {NULL, NULL}
+};
+
+void nerv_point_init(lua_State *L) {
+    /* create a class and let luaT know */
+    luaT_newmetatable(L, point_tname, NULL, point_new, NULL, NULL);
+    /* register member functions */
+    luaL_register(L, NULL, point_methods);
+    /* keep the stack balanced, see `nerv.c` */
+    lua_pop(L, 1);
+}
+
+void nerv_better_point_init(lua_State *L) {
+    /* create a class and let luaT know */
+    luaT_newmetatable(L, better_point_tname, point_tname,
+                        better_point_new, NULL, NULL);
+    /* register member functions */
+    luaL_register(L, NULL, better_point_methods);
+    /* keep the stack balanced, see `nerv.c` */
+    lua_pop(L, 1);
+}
+
+void nerv_example_init(lua_State *L) {
+    nerv_point_init(L);
+    nerv_better_point_init(L);
+}