From 924bb8b00e801d64dcfa11b434abc0c63a70f654 Mon Sep 17 00:00:00 2001
From: beder <jbeder@gmail.com>
Date: Thu, 12 Jan 2012 01:03:31 -0600
Subject: [PATCH] Added default parameters for the as<> function (new API)

---
 include/yaml-cpp/node/impl.h | 81 +++++++++++++++++++++++++++++-------
 include/yaml-cpp/node/node.h |  2 +
 test/new-api/nodetests.cpp   | 13 ++++++
 3 files changed, 81 insertions(+), 15 deletions(-)

diff --git a/include/yaml-cpp/node/impl.h b/include/yaml-cpp/node/impl.h
index e379461..b58b394 100644
--- a/include/yaml-cpp/node/impl.h
+++ b/include/yaml-cpp/node/impl.h
@@ -65,26 +65,77 @@ namespace YAML
 	}
 	
 	// access
+    
+    // template helpers
+    template<typename T, typename S>
+    struct as_if {
+        explicit as_if(const Node& node_): node(node_) {}
+        const Node& node;
+        
+        const T operator()(const S& fallback) const {
+            if(!node.m_pNode)
+                return fallback;
+            
+            T t;
+            if(convert<T>::decode(node, t))
+                return t;
+            return fallback;
+        }
+    };
+    
+    template<typename S>
+    struct as_if<std::string, S> {
+        explicit as_if(const Node& node_): node(node_) {}
+        const Node& node;
+        
+        const std::string operator()(const S& fallback) const {
+            if(node.Type() != NodeType::Scalar)
+                return fallback;
+            return node.Scalar();
+        }
+    };
+    
+    template<typename T>
+    struct as_if<T, void> {
+        explicit as_if(const Node& node_): node(node_) {}
+        const Node& node;
+        
+        const T operator()() const {
+            if(!node.m_pNode)
+                throw std::runtime_error("Unable to convert to type");
+			
+            T t;
+            if(convert<T>::decode(node, t))
+                return t;
+            throw std::runtime_error("Unable to convert to type");
+        }
+    };
+    
+    template<>
+    struct as_if<std::string, void> {
+        explicit as_if(const Node& node_): node(node_) {}
+        const Node& node;
+        
+        const std::string operator()() const {
+            if(node.Type() != NodeType::Scalar)
+                throw std::runtime_error("Unable to convert to string, not a scalar");
+            return node.Scalar();
+        }
+    };
+    
+    // access functions
 	template<typename T>
 	inline const T Node::as() const
 	{
-		if(!m_pNode)
-			throw std::runtime_error("Unable to convert to type");
-			
-		T t;
-		if(convert<T>::decode(*this, t))
-			return t;
-		throw std::runtime_error("Unable to convert to type");
-	}
-	
-	template<>
-	inline const std::string Node::as() const
-	{
-		if(Type() != NodeType::Scalar)
-			throw std::runtime_error("Unable to convert to string, not a scalar");
-		return Scalar();
+        return as_if<T, void>(*this)();
 	}
 
+    template<typename T, typename S>
+    inline const T Node::as(const S& fallback) const
+    {
+        return as_if<T, S>(*this)(fallback);
+    }
+    
 	inline const std::string& Node::Scalar() const
 	{
 		return m_pNode ? m_pNode->scalar() : detail::node_data::empty_scalar;
diff --git a/include/yaml-cpp/node/node.h b/include/yaml-cpp/node/node.h
index 8066057..9445624 100644
--- a/include/yaml-cpp/node/node.h
+++ b/include/yaml-cpp/node/node.h
@@ -22,6 +22,7 @@ namespace YAML
 		friend class NodeEvents;
 		friend class detail::node_data;
 		template<typename> friend class detail::iterator_base;
+        template<typename T, typename S> friend struct as_if;
 		
 		Node();
 		explicit Node(NodeType::value type);
@@ -43,6 +44,7 @@ namespace YAML
 		
 		// access
 		template<typename T> const T as() const;
+		template<typename T, typename S> const T as(const S& fallback) const;
 		const std::string& Scalar() const;
 		const std::string& Tag() const;
 		void SetTag(const std::string& tag);
diff --git a/test/new-api/nodetests.cpp b/test/new-api/nodetests.cpp
index c41afed..74f92ae 100644
--- a/test/new-api/nodetests.cpp
+++ b/test/new-api/nodetests.cpp
@@ -286,6 +286,18 @@ namespace Test
             node = YAML::Node();
             return true;
         }
+        
+        TEST FallbackValues()
+        {
+            YAML::Node node = YAML::Load("foo: bar\nx: 2");
+            YAML_ASSERT(node["foo"].as<std::string>() == "bar");
+            YAML_ASSERT(node["foo"].as<std::string>("hello") == "bar");
+            YAML_ASSERT(node["baz"].as<std::string>("hello") == "hello");
+            YAML_ASSERT(node["x"].as<int>() == 2);
+            YAML_ASSERT(node["x"].as<int>(5) == 2);
+            YAML_ASSERT(node["y"].as<int>(5) == 5);
+            return true;
+        }
 	}
 	
 	void RunNodeTest(TEST (*test)(), const std::string& name, int& passed, int& total) {
@@ -332,6 +344,7 @@ namespace Test
 		RunNodeTest(&Node::Bool, "bool", passed, total);
 		RunNodeTest(&Node::AutoBoolConversion, "auto bool conversion", passed, total);
 		RunNodeTest(&Node::Reassign, "reassign", passed, total);
+		RunNodeTest(&Node::FallbackValues, "fallback values", passed, total);
 
 		std::cout << "Node tests: " << passed << "/" << total << " passed\n";
 		return passed == total;