add array element proxy support

janssonxx.h

@@ -21,6 +21,7 @@ namespace jansson {
 
 	class Iterator;
 	class Value;
+	class _ArrayProxy;
 
 	// base class for JSON value interface
 	template <typename _Base>
@@ -35,6 +36,9 @@ namespace jansson {
 		// create reference to value
 		_ValueBase(json_t* json) : _Base(json) {}
 
+		// assignment operator
+		_ValueBase& operator=(const Value& value) { _Base::operator=(value); return *this; }
+
 		// check value type
 		bool is_undefined() const { return _Base::as_json() == 0; }
 		bool is_object() const { return json_is_object(_Base::as_json()); }
@@ -62,14 +66,14 @@ namespace jansson {
 		inline const Value operator[](unsigned long index) const;
 
 		// get value at array index (non-const version)
-		inline Value at(unsigned int index);
+		inline _ValueBase<_ArrayProxy> at(unsigned int index);
 
-		inline Value operator[](signed int index);
+		inline _ValueBase<_ArrayProxy> operator[](signed int index);
-		inline Value operator[](unsigned int index);
+		inline _ValueBase<_ArrayProxy> operator[](unsigned int index);
-		inline Value operator[](signed short index);
+		inline _ValueBase<_ArrayProxy> operator[](signed short index);
-		inline Value operator[](unsigned short index);
+		inline _ValueBase<_ArrayProxy> operator[](unsigned short index);
-		inline Value operator[](signed long index);
+		inline _ValueBase<_ArrayProxy> operator[](signed long index);
-		inline Value operator[](unsigned long index);
+		inline _ValueBase<_ArrayProxy> operator[](unsigned long index);
 
 		// get object property
 		inline const Value get(const char* key) const;
@@ -149,6 +153,29 @@ namespace jansson {
 		json_t* _value;
 	};
 
+	// proxies an array element
+	class _ArrayProxy {
+	public:
+		// construct new Value with an undefined value
+		_ArrayProxy() : _array(0), _index(0) {}
+
+		// constructor
+		_ArrayProxy(json_t* array, unsigned int index) : _array(array), _index(index) {}
+
+		// assign to the proxied element
+		inline _ArrayProxy& operator=(const Value& value);
+
+		// get the proxied element
+		json_t* as_json() const { return json_array_get(_array, _index); }
+
+	private:
+		// array object we wrap
+		json_t* _array;
+
+		// index of property
+		unsigned int _index;
+	};
+
 	// represents any JSON value
 	class Value : public _ValueBase<_Value> {
 	public:

janssonxx.tcc

@@ -28,22 +28,22 @@ const jansson::Value jansson::_ValueBase<_Base>::operator[](unsigned long index)
 
 // get value at array index (non-const version)
 template <typename _Base>
-jansson::Value jansson::_ValueBase<_Base>::at(unsigned int index) {
+jansson::_ValueBase<jansson::_ArrayProxy> jansson::_ValueBase<_Base>::at(unsigned int index) {
-	return jansson::Value(json_array_get(_Base::as_json(), index));
+	return _ArrayProxy(_Base::as_json(), index);
 }
 
 template <typename _Base>
-jansson::Value jansson::_ValueBase<_Base>::operator[](signed int index) { return at(index); }
+jansson::_ValueBase<jansson::_ArrayProxy> jansson::_ValueBase<_Base>::operator[](signed int index) { return at(index); }
 template <typename _Base>
-jansson::Value jansson::_ValueBase<_Base>::operator[](unsigned int index) { return at(index); }
+jansson::_ValueBase<jansson::_ArrayProxy> jansson::_ValueBase<_Base>::operator[](unsigned int index) { return at(index); }
 template <typename _Base>
-jansson::Value jansson::_ValueBase<_Base>::operator[](signed short index) { return at(index); }
+jansson::_ValueBase<jansson::_ArrayProxy> jansson::_ValueBase<_Base>::operator[](signed short index) { return at(index); }
 template <typename _Base>
-jansson::Value jansson::_ValueBase<_Base>::operator[](unsigned short index) { return at(index); }
+jansson::_ValueBase<jansson::_ArrayProxy> jansson::_ValueBase<_Base>::operator[](unsigned short index) { return at(index); }
 template <typename _Base>
-jansson::Value jansson::_ValueBase<_Base>::operator[](signed long index) { return at(index); }
+jansson::_ValueBase<jansson::_ArrayProxy> jansson::_ValueBase<_Base>::operator[](signed long index) { return at(index); }
 template <typename _Base>
-jansson::Value jansson::_ValueBase<_Base>::operator[](unsigned long index) { return at(index); }
+jansson::_ValueBase<jansson::_ArrayProxy> jansson::_ValueBase<_Base>::operator[](unsigned long index) { return at(index); }
 
 // get object property
 template <typename _Base>
@@ -131,3 +131,9 @@ template <typename _Base>
 	json_array_insert(_Base::as_json(), index, value._Base::as_json());
 	return *this;
 }
+
+// assign value to proxied array element
+jansson::_ArrayProxy& jansson::_ArrayProxy::operator=(const Value& value) {
+	json_array_set(_array, _index, value.as_json());
+	return *this;
+}

test.cc

@@ -149,7 +149,13 @@ int main() {
 	e14.set_key("foo", jansson::Value::object());
 	ASSERT_TRUE(e14["foo"].is_object(), "e14.foo is not an object after assignment");
 	//e14["foo"]["bar"] = jansson::Value::from(42);
-	//ASSERT_EQ(e14["foo"]["bar"].as_integer(), 42, "e14.foo.bar has incorrecy value after assignment");
+	//ASSERT_EQ(e14["foo"]["bar"].as_integer(), 42, "e14.foo.bar has incorrect value after assignment");
 
+	jansson::Value e15(jansson::Value::array());
+	ASSERT_TRUE(e15.is_array(), "e15 is not an array after construction");
+	e15.set_at(0, jansson::Value::from(42));
+	ASSERT_EQ(e15[0].as_integer(), 42, "e15[0] has incorrect value after assignment");
+	e15[0] = jansson::Value::from("foo");
+	ASSERT_EQ(e15[0].as_string(), "foo", "e15[0] has incorrecy value after assignment");
 	return 0;
 }