Descendents of class Exception are used to communicate between raise methods and rescue statements in begin/end blocks. Exception objects carry information about the exception—its type (the exception’s class name), an optional descriptive string, and optional traceback information. Programs may subclass Exception to add additional information.

Methods
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N
Class Public methods
NoMethodError.new(msg, name [, args]) => no_method_error

Construct a NoMethodError exception for a method of the given name called with the given arguments. The name may be accessed using the name method on the resulting object, and the arguments using the args method.

Source: show 

static VALUE
nometh_err_initialize(argc, argv, self)
    int argc;
    VALUE *argv;
    VALUE self;
{
    VALUE args = (argc > 2) ? argv[--argc] : Qnil;
    name_err_initialize(argc, argv, self);
    rb_iv_set(self, "args", args);
    return self;
}
Instance Public methods
no_method_error.args => obj

Return the arguments passed in as the third parameter to the constructor.

Source: show 

static VALUE
nometh_err_args(self)
    VALUE self;
{
    return rb_attr_get(self, rb_intern("args"));
}