From 84feb4bd87d37f726b0b54816dd0ee097450e3ca Mon Sep 17 00:00:00 2001
From: Jarryd Beck <jarro.2783@gmail.com>
Date: Mon, 19 Nov 2018 17:45:51 +1100
Subject: [PATCH] Throw in ParseResult::as when option isn't present

Fixes #124.
---
 CHANGELOG.md        | 1 +
 include/cxxopts.hpp | 4 ++++
 test/options.cpp    | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fb92e62..185ab21 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ options. The project adheres to semantic versioning.
 * Fix version numbering in CMakeLists.txt
 * Remove unused declaration of the undefined `ParseResult::get_option`.
 * Throw on invalid option syntax when beginning with a `-`.
+* Throw in `as` when option wasn't present.
 
 ## 2.1.1
 
diff --git a/include/cxxopts.hpp b/include/cxxopts.hpp
index 6fd170d..6677002 100644
--- a/include/cxxopts.hpp
+++ b/include/cxxopts.hpp
@@ -1048,6 +1048,10 @@ namespace cxxopts
     const T&
     as() const
     {
+      if (m_value == nullptr) {
+        throw std::domain_error("No value");
+      }
+
 #ifdef CXXOPTS_NO_RTTI
       return static_cast<const values::standard_value<T>&>(*m_value).get();
 #else
diff --git a/test/options.cpp b/test/options.cpp
index 1f37172..a54be10 100644
--- a/test/options.cpp
+++ b/test/options.cpp
@@ -53,6 +53,7 @@ TEST_CASE("Basic options", "[options]")
     ("a,av", "a short option with a value", cxxopts::value<std::string>())
     ("6,six", "a short number option")
     ("p, space", "an option with space between short and long")
+    ("nothing", "won't exist", cxxopts::value<std::string>())
     ;
 
   Argv argv({
@@ -92,6 +93,8 @@ TEST_CASE("Basic options", "[options]")
   CHECK(arguments[1].key() == "short");
   CHECK(arguments[2].key() == "value");
   CHECK(arguments[3].key() == "av");
+  
+  CHECK_THROWS_AS(result["nothing"].as<std::string>(), std::domain_error);
 }
 
 TEST_CASE("Short options", "[options]")