method

const_get

v2_1_10 - Show latest stable - 0 notes - Class: Module

const_get(p1, p2 = v2) public

Checks for a constant with the given name in mod. If inherit is set, the lookup will also search the ancestors (and Object if mod is a Module).

The value of the constant is returned if a definition is found, otherwise a NameError is raised.

Math.const_get(:PI)   #=> 3.14159265358979

This method will recursively look up constant names if a namespaced class name is provided. For example:

module Foo; class Bar; end end
Object.const_get 'Foo::Bar'

The inherit flag is respected on each lookup. For example:

module Foo
  class Bar
    VAL = 10
  end

  class Baz < Bar; end
end

Object.const_get 'Foo::Baz::VAL'         # => 10
Object.const_get 'Foo::Baz::VAL', false  # => NameError

If the argument is not a valid constant name a NameError will be raised with a warning “wrong constant name”.

Object.const_get 'foobar' #=> NameError: wrong constant name foobar

Show source

static VALUE
rb_mod_const_get(int argc, VALUE *argv, VALUE mod)
{
    VALUE name, recur;
    rb_encoding *enc;
    const char *pbeg, *p, *path, *pend;
    ID id;

    if (argc == 1) {
        name = argv[0];
        recur = Qtrue;
    }
    else {
        rb_scan_args(argc, argv, "11", &name, &recur);
    }

    if (SYMBOL_P(name)) {
        id = SYM2ID(name);
        if (!rb_is_const_id(id)) goto wrong_id;
        return RTEST(recur) ? rb_const_get(mod, id) : rb_const_get_at(mod, id);
    }

    path = StringValuePtr(name);
    enc = rb_enc_get(name);

    if (!rb_enc_asciicompat(enc)) {
        rb_raise(rb_eArgError, "invalid class path encoding (non ASCII)");
    }

    pbeg = p = path;
    pend = path + RSTRING_LEN(name);

    if (p >= pend || !*p) {
      wrong_name:
        rb_raise(rb_eNameError, "wrong constant name %"PRIsVALUE,
                 QUOTE(name));
    }

    if (p + 2 < pend && p[0] == ':' && p[1] == ':') {
        mod = rb_cObject;
        p += 2;
        pbeg = p;
    }

    while (p < pend) {
        VALUE part;
        long len, beglen;

        while (p < pend && *p != ':') p++;

        if (pbeg == p) goto wrong_name;

        id = rb_check_id_cstr(pbeg, len = p-pbeg, enc);
        beglen = pbeg-path;

        if (p < pend && p[0] == ':') {
            if (p + 2 >= pend || p[1] != ':') goto wrong_name;
            p += 2;
            pbeg = p;
        }

        if (!RB_TYPE_P(mod, T_MODULE) && !RB_TYPE_P(mod, T_CLASS)) {
            rb_raise(rb_eTypeError, "%"PRIsVALUE" does not refer to class/module",
                     QUOTE(name));
        }

        if (!id) {
            part = rb_str_subseq(name, beglen, len);
            OBJ_FREEZE(part);
            if (!ISUPPER(*pbeg) || !rb_is_const_name(part)) {
                rb_name_error_str(part, "wrong constant name %"PRIsVALUE,
                                  QUOTE(part));
            }
            else if (!rb_method_basic_definition_p(CLASS_OF(mod), id_const_missing)) {
                id = rb_intern_str(part);
            }
            else {
                rb_name_error_str(part, "uninitialized constant %"PRIsVALUE"%"PRIsVALUE,
                                  rb_str_subseq(name, 0, beglen),
                                  QUOTE(part));
            }
        }
        if (!rb_is_const_id(id)) {
          wrong_id:
            rb_name_error(id, "wrong constant name %"PRIsVALUE,
                          QUOTE_ID(id));
        }
        mod = RTEST(recur) ? rb_const_get(mod, id) : rb_const_get_at(mod, id);
    }

    return mod;
}

const_get

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