Method: Hash#keys

Defined in:
hash.c

#keys ⇒ Array

Returns a new array populated with the keys from this hash. See also Hash#values.

h = { "a" => 100, "b" => 200, "c" => 300, "d" => 400 }
h.keys   #=> ["a", "b", "c", "d"]

Returns:



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# File 'hash.c', line 1760

VALUE
rb_hash_keys(VALUE hash)
{
    VALUE keys;
    st_index_t size = RHASH_SIZE(hash);

    keys = rb_ary_new_capa(size);
    if (size == 0) return keys;

    if (ST_DATA_COMPATIBLE_P(VALUE)) {
	st_table *table = RHASH(hash)->ntbl;

	if (OBJ_PROMOTED(keys)) rb_gc_writebarrier_remember_promoted(keys);
	RARRAY_PTR_USE(keys, ptr, {
	    size = st_keys_check(table, ptr, size, Qundef);
	});
	rb_ary_set_len(keys, size);
    }
    else {
	rb_hash_foreach(hash, keys_i, keys);
    }

    return keys;
}