`FuncLogin': undefined method `has_key?' for nil:NilClass (NoMethodError)

class User
attr_accessor :login, :password

@contas = {"admin" => "pass"}

def initialize(login, password)
    @login    = login
    @password = password
end

def FuncLogin
    if @contas.has_key?(@login)
        if contas[@login] == @password
            return "Logado"
        else
            puts "Senha incorreta."
        end
    else
        return "Login inexistente."
    end
end
end