Hash#key

(V) -> K?

hash.key(value) → key or nil

static VALUE
rb_hash_key(VALUE hash, VALUE value)
{
    VALUE args[2];

    args[0] = value;
    args[1] = Qnil;

    rb_hash_foreach(hash, key_i, (VALUE)args);

    return args[1];
}

Returns the key for the first-found entry with the given value (see Entry Order):

Example

h = {foo: 0, bar: 2, baz: 2}
h.key(0) # => :foo
h.key(2) # => :bar

Returns nil if no such value is found.

See also #key? #keep_if #invert #keys also in 4.1 · 4.0 · 3.3 · 3.2 · 3.1 · 3.0

‹ prev#keep_if next ›#key?