From: nobuyoshi nakada <nobuyoshi.nakada@...>
Date: 2005-06-24T18:21:50+09:00
Subject: Re: string to Class object

Hi,

At Fri, 24 Jun 2005 16:07:18 +0900,
Mark Hubbart wrote in [ruby-talk:146353]:
> What about adding a Kernel#const_get that does this? That might
> separate things a little better; a global method that decodes any
> class name, nested or not, based on current context.

Kernel also is one of modules.

  $ ruby -e 'p Kernel.const_get("Object")'
  Object


Index: object.c
===================================================================
RCS file: /cvs/ruby/src/ruby/object.c,v
retrieving revision 1.169
diff -U2 -p -r1.169 object.c
--- object.c	11 May 2005 07:00:32 -0000	1.169
+++ object.c	24 Jun 2005 04:37:33 -0000
@@ -1715,9 +1715,46 @@ rb_mod_attr_accessor(argc, argv, klass)
 }
 
+static ID
+mod_const_id(namep)
+    volatile VALUE *namep;
+{
+    VALUE tmp, name = *namep;
+    ID id;
+
+    switch (TYPE(name)) {
+      case T_STRING:
+	break;
+      case T_FIXNUM:
+	rb_warn("do not use Fixnums as Symbols");
+	id = FIX2LONG(name);
+	if (!rb_id2name(id)) {
+	    rb_raise(rb_eArgError, "%ld is not a symbol", id);
+	}
+	return id;
+      case T_SYMBOL:
+	return SYM2ID(name);
+      default:
+	tmp = rb_check_string_type(name);
+	if (NIL_P(tmp)) {
+	    rb_raise(rb_eTypeError, "%s is not a symbol", RSTRING(rb_inspect(name))->ptr);
+	}
+	*namep = name = tmp;
+    }
+    if (RSTRING(name)->ptr && strchr(RSTRING(name)->ptr, ':'))
+	return 0;
+
+    id = str_to_id(name);
+    if (!rb_is_const_id(id)) {
+	rb_name_error(id, "wrong constant name %s", rb_id2name(id));
+    }
+
+    return id;
+}
+
 /*
  *  call-seq:
  *     mod.const_get(sym)    => obj
  *  
- *  Returns the value of the named constant in <i>mod</i>.
+ *  Returns the value of the named constant under <i>mod</i>.
  *     
  *     Math.const_get(:PI)   #=> 3.14159265358979
@@ -1728,9 +1765,10 @@ rb_mod_const_get(mod, name)
     VALUE mod, name;
 {
-    ID id = rb_to_id(name);
+    ID id = mod_const_id(&name);
 
-    if (!rb_is_const_id(id)) {
-	rb_name_error(id, "wrong constant name %s", rb_id2name(id));
+    if (!id) {
+	return rb_path2const(RSTRING(name)->ptr, mod, Qtrue);
     }
+
     return rb_const_get(mod, id);
 }
Index: variable.c
===================================================================
RCS file: /cvs/ruby/src/ruby/variable.c,v
retrieving revision 1.121
diff -U2 -p -r1.121 variable.c
--- variable.c	13 May 2005 08:56:14 -0000	1.121
+++ variable.c	24 Jun 2005 04:17:48 -0000
@@ -234,11 +234,21 @@ rb_set_class_path(klass, under, name)
 
 VALUE
-rb_path2class(path)
+rb_path2const(path, cbase, idcheck)
     const char *path;
+    VALUE cbase;
+    int idcheck;
 {
     const char *pbeg, *p;
     ID id;
-    VALUE c = rb_cObject;
+    VALUE c = cbase;
 
+    switch (TYPE(cbase)) {
+      case T_MODULE:
+      case T_CLASS:
+	break;
+      default:
+	rb_raise(rb_eTypeError, "class or module required but %s given",
+		 rb_obj_classname(cbase));
+    }
     if (path[0] == '#') {
 	rb_raise(rb_eArgError, "can't retrieve anonymous class %s", path);
@@ -249,6 +259,9 @@ rb_path2class(path)
 
 	while (*p && *p != ':') p++;
-	str = rb_str_new(pbeg, p-pbeg);
+	*(volatile VALUE *)&str = rb_str_new(pbeg, p-pbeg);
 	id = rb_intern(RSTRING(str)->ptr);
+	if (idcheck && !rb_is_const_id(id)) {
+	    rb_name_error(id, "wrong constant name %s", RSTRING(str)->ptr);
+	}
 	if (p[0] == ':') {
 	    if (p[1] != ':') goto undefined_class;
@@ -258,7 +271,15 @@ rb_path2class(path)
 	if (!rb_const_defined(c, id)) {
 	  undefined_class:
-	    rb_raise(rb_eArgError, "undefined class/module %.*s", p-path, path);
+	    if (cbase == rb_cObject) {
+		rb_raise(rb_eArgError, "undefined class/module %s",
+			 RSTRING(str)->ptr);
+	    }
+	    else {
+		rb_raise(rb_eArgError, "undefined class/module %s under %s",
+			 RSTRING(str)->ptr, rb_class2name(c));
+	    }
 	}
 	c = rb_const_get_at(c, id);
+	if (!*p) break;
 	switch (TYPE(c)) {
 	  case T_MODULE:
@@ -273,4 +294,21 @@ rb_path2class(path)
 }
 
+VALUE
+rb_path2class(path)
+    const char *path;
+{
+    VALUE c = rb_path2const(path, rb_cObject, Qfalse);
+
+    switch (TYPE(c)) {
+      case T_MODULE:
+      case T_CLASS:
+	break;
+      default:
+	rb_raise(rb_eTypeError, "%s does not refer class/module", path);
+    }
+
+    return c;
+}
+
 void
 rb_name_class(klass, id)
Index: intern.h
===================================================================
RCS file: /cvs/ruby/src/ruby/intern.h,v
retrieving revision 1.170
diff -U2 -p -r1.170 intern.h
--- intern.h	12 Jun 2005 16:56:05 -0000	1.170
+++ intern.h	24 Jun 2005 03:57:26 -0000
@@ -504,6 +504,7 @@
 VALUE rb_mod_name _((VALUE));
 VALUE rb_class_path _((VALUE));
 void rb_set_class_path _((VALUE, VALUE, const char*));
+VALUE rb_path2const _((const char*, VALUE, int));
 VALUE rb_path2class _((const char*));
 void rb_name_class _((VALUE, ID));
 VALUE rb_class_name _((VALUE));


-- 
Nobu Nakada