Mutable v2

json11.cpp

@@ -131,6 +131,27 @@ void Json::dump(string &out) const {
     m_ptr->dump(out);
 }
 
+/* * * * * * * * * * * * * * * * * * * *
+ * Indexed wrapper to prevent autovivification
+ */
+
+JsonIndex::JsonIndex(Json obj, const std::string & key)
+{
+    m_object = obj;
+    m_key = key;
+}
+
+Json & JsonIndex::operator =(const Json & value)
+{
+    auto & obj = m_object.object_items();
+    return obj[m_key] = value;
+}
+
+JsonIndex::operator Json()
+{
+    return m_object[m_key];
+}
+
 /* * * * * * * * * * * * * * * * * * * *
  * Value wrappers
  */
@@ -156,7 +177,7 @@ protected:
         return m_value < static_cast<const Value<tag, T> *>(other)->m_value;
     }
 
-    const T m_value;
+    T m_value;
     void dump(string &out) const override { json11::dump(m_value, out); }
 };
 
@@ -236,16 +257,16 @@ public:
 };
 
 class JsonArray final : public Value<Json::ARRAY, Json::array> {
-    const Json::array &array_items() const override { return m_value; }
+    Json::array &array_items() override { return m_value; }
-    const Json & operator[](size_t i) const override;
+    Json & operator[](size_t i) override;
 public:
     explicit JsonArray(const Json::array &value) : Value(value) {}
     explicit JsonArray(Json::array &&value)      : Value(move(value)) {}
 };
 
 class JsonObject final : public Value<Json::OBJECT, Json::object> {
-    const Json::object &object_items() const override { return m_value; }
+    Json::object &object_items() override { return m_value; }
-    const Json & operator[](const string &key) const override;
+    Json & operator[](const string &key) override;
 public:
     explicit JsonObject(const Json::object &value) : Value(value) {}
     explicit JsonObject(Json::object &&value)      : Value(move(value)) {}
@@ -320,14 +341,14 @@ Json::Json(Json::object &&values)      : m_ptr(make_shared<JsonObject>(move(valu
 Json::Type Json::type()                           const { return m_ptr->type();         }
 double Json::number_value()                       const { return m_ptr->number_value(); }
 int64_ Json::int64_value()                        const { return m_ptr->int64_value();  }
-uint64_ Json::uint64_value()                        const { return m_ptr->uint64_value();  }
+uint64_ Json::uint64_value()                      const { return m_ptr->uint64_value();  }
 bool Json::bool_value()                           const { return m_ptr->bool_value();   }
 string Json::as_string()                          const { return m_ptr->as_string(); }
 const string & Json::string_value()               const { return m_ptr->string_value(); }
-const vector<Json> & Json::array_items()          const { return m_ptr->array_items();  }
+vector<Json> & Json::array_items()                      { return m_ptr->array_items();  }
-const map<string, Json> & Json::object_items()    const { return m_ptr->object_items(); }
+map<string, Json> & Json::object_items()                { return m_ptr->object_items(); }
-const Json & Json::operator[] (size_t i)          const { return (*m_ptr)[i];           }
+Json & Json::operator[] (size_t i)                      { return (*m_ptr)[i];           }
-const Json & Json::operator[] (const string &key) const { return (*m_ptr)[key];         }
+Json & Json::operator[] (const string &key)             { return (*m_ptr)[key];         }
 
 double                    JsonValue::number_value()              const { return 0; }
 int64_                    JsonValue::int64_value()               const { return 0; }
@@ -335,16 +356,16 @@ uint64_                   JsonValue::uint64_value()              const { return
 bool                      JsonValue::bool_value()                const { return false; }
 string                    JsonValue::as_string()                 const { return statics().empty_string; }
 const string &            JsonValue::string_value()              const { return statics().empty_string; }
-const vector<Json> &      JsonValue::array_items()               const { return statics().empty_vector; }
+vector<Json> &            JsonValue::array_items()                     { return statics().empty_vector; }
-const map<string, Json> & JsonValue::object_items()              const { return statics().empty_map; }
+map<string, Json> &       JsonValue::object_items()                    { return statics().empty_map; }
-const Json &              JsonValue::operator[] (size_t)         const { return static_null(); }
+Json &                    JsonValue::operator[] (size_t)               { return static_null(); }
-const Json &              JsonValue::operator[] (const string &) const { return static_null(); }
+Json &                    JsonValue::operator[] (const string &)       { return static_null(); }
 
-const Json & JsonObject::operator[] (const string &key) const {
+Json & JsonObject::operator[] (const string &key) {
     auto iter = m_value.find(key);
     return (iter == m_value.end()) ? static_null() : iter->second;
 }
-const Json & JsonArray::operator[] (size_t i) const {
+Json & JsonArray::operator[] (size_t i) {
     if (i >= m_value.size()) return static_null();
     else return m_value[i];
 }

json11.hpp

@@ -150,7 +150,7 @@ public:
     int64_ int64_value() const;
     uint64_ uint64_value() const;
 
-    // Return the enclosed string if this is a string, "" otherwise.
+    // Return the enclosed value as string.
     std::string as_string() const;
 
     // Return the enclosed value if this is a boolean, false otherwise.
@@ -158,14 +158,14 @@ public:
     // Return the enclosed string if this is a string, "" otherwise.
     const std::string &string_value() const;
     // Return the enclosed std::vector if this is an array, or an empty vector otherwise.
-    const array &array_items() const;
+    array &array_items();
     // Return the enclosed std::map if this is an object, or an empty map otherwise.
-    const object &object_items() const;
+    object &object_items();
 
     // Return a reference to arr[i] if this is an array, Json() otherwise.
-    const Json & operator[](size_t i) const;
+    Json & operator[](size_t i);
     // Return a reference to obj[key] if this is an object, Json() otherwise.
-    const Json & operator[](const std::string &key) const;
+    Json & operator[](const std::string &key);
 
     // Serialize.
     void dump(std::string &out) const;
@@ -220,9 +220,20 @@ public:
     bool has_shape(const shape & types, std::string & err) const;
 
 private:
+    friend class JsonIndex;
     std::shared_ptr<JsonValue> m_ptr;
 };
 
+class JsonIndex {
+protected:
+    Json m_object;
+    std::string m_key;
+public:
+    JsonIndex(Json obj, const std::string & key);
+    Json &operator = (const Json & value);
+    operator Json ();
+};
+
 // Internal class hierarchy - JsonValue objects are not exposed to users of this API.
 class JsonValue {
 protected:
@@ -240,10 +251,10 @@ protected:
     virtual bool bool_value() const;
     virtual const std::string &string_value() const;
     virtual std::string as_string() const;
-    virtual const Json::array &array_items() const;
+    virtual Json::array &array_items();
-    virtual const Json &operator[](size_t i) const;
+    virtual Json &operator[](size_t i);
-    virtual const Json::object &object_items() const;
+    virtual Json::object &object_items();
-    virtual const Json &operator[](const std::string &key) const;
+    virtual Json &operator[](const std::string &key);
     virtual ~JsonValue() {}
 };