class KeyError

Raised when the specified key is not found. It is a subclass of IndexError.

h = {"foo" => :bar}
h.fetch("foo") #=> :bar
h.fetch("baz") #=> KeyError: key not found: "baz"

Public Class Methods

new(message=nil, receiver: nil, key: nil) → key_error click to toggle source

Construct a new KeyError exception with the given message, receiver and key.

static VALUE
key_err_initialize(int argc, VALUE *argv, VALUE self)
    VALUE options;

    rb_call_super(rb_scan_args(argc, argv, "01:", NULL, &options), argv);

    if (!NIL_P(options)) {
        ID keywords[2];
        VALUE values[numberof(keywords)];
        int i;
        keywords[0] = id_receiver;
        keywords[1] = id_key;
        rb_get_kwargs(options, keywords, 0, numberof(values), values);
        for (i = 0; i < numberof(values); ++i) {
            if (!UNDEF_P(values[i])) {
                rb_ivar_set(self, keywords[i], values[i]);

    return self;

Public Instance Methods

key → object click to toggle source

Return the key caused this KeyError exception.

static VALUE
key_err_key(VALUE self)
    VALUE key;

    key = rb_ivar_lookup(self, id_key, Qundef);
    if (!UNDEF_P(key)) return key;
    rb_raise(rb_eArgError, "no key is available");
receiver → object click to toggle source

Return the receiver associated with this KeyError exception.

static VALUE
key_err_receiver(VALUE self)
    VALUE recv;

    recv = rb_ivar_lookup(self, id_receiver, Qundef);
    if (!UNDEF_P(recv)) return recv;
    rb_raise(rb_eArgError, "no receiver is available");