Method: Hash.[]

Defined in:

hash.c

.[](key, value, ...) ⇒ Object .[]([ [key, value)) ⇒ Object .[](object) ⇒ Object

Creates a new hash populated with the given objects.

Similar to the literal { key => value, ... }. In the first form, keys and values occur in pairs, so there must be an even number of arguments.

The second and third form take a single argument which is either an array of key-value pairs or an object convertible to a hash.

Hash["a", 100, "b", 200]             #=> {"a"=>100, "b"=>200}
Hash[ [ ["a", 100], ["b", 200] ] ]   #=> {"a"=>100, "b"=>200}
Hash["a" => 100, "b" => 200]         #=> {"a"=>100, "b"=>200}

# File 'hash.c', line 495

static VALUE
rb_hash_s_create(int argc, VALUE *argv, VALUE klass)
{
    VALUE hash, tmp;
    int i;

    if (argc == 1) {
	tmp = rb_hash_s_try_convert(Qnil, argv[0]);
	if (!NIL_P(tmp)) {
	    hash = hash_alloc(klass);
	    if (RHASH(tmp)->ntbl) {
		RHASH(hash)->ntbl = st_copy(RHASH(tmp)->ntbl);
	    }
	    return hash;
	}

	tmp = rb_check_array_type(argv[0]);
	if (!NIL_P(tmp)) {
	    long i;

	    hash = hash_alloc(klass);
	    for (i = 0; i < RARRAY_LEN(tmp); ++i) {
		VALUE e = RARRAY_AREF(tmp, i);
		VALUE v = rb_check_array_type(e);
		VALUE key, val = Qnil;

		if (NIL_P(v)) {
#if 0 /* refix in the next release */
		    rb_raise(rb_eArgError, "wrong element type %s at %ld (expected array)",
			     rb_builtin_class_name(e), i);

#else
		    rb_warn("wrong element type %s at %ld (expected array)",
			    rb_builtin_class_name(e), i);
		    rb_warn("ignoring wrong elements is deprecated, remove them explicitly");
		    rb_warn("this causes ArgumentError in the next release");
		    continue;
#endif
		}
		switch (RARRAY_LEN(v)) {
		  default:
		    rb_raise(rb_eArgError, "invalid number of elements (%ld for 1..2)",
			     RARRAY_LEN(v));
		  case 2:
		    val = RARRAY_AREF(v, 1);
		  case 1:
		    key = RARRAY_AREF(v, 0);
		    rb_hash_aset(hash, key, val);
		}
	    }
	    return hash;
	}
    }
    if (argc % 2 != 0) {
	rb_raise(rb_eArgError, "odd number of arguments for Hash");
    }

    hash = hash_alloc(klass);
    for (i=0; i<argc; i+=2) {
        rb_hash_aset(hash, argv[i], argv[i + 1]);
    }

    return hash;
}