c++ How to serialize class to json and parse the json file? - c++

Question

I have an xObject Class which basically is a trivial "Person" Class and I want to be able to serialize the whole class to a .json file, and then read that file in order to be able to extract the variables from the file and link those variables to the name of the class.
So for example:
xObject Class Code:
class xObject{
string name;
string lastname;
int age;
public:
string getName(){
return name;
}
string getLastname(){
return lastname;
}
int getAge(){
return age;
}
}
And then I create an object with some attributes on it.
int main(){
xObject homer;
homer.name = "Homer";
homer.lastname = "Simpson";
homer.age = 30;
//SERIALIZATION OF HOMER.
homer.serialExport("File.json")
return 0;
}
So now, my File.json should look like this:
{"homer" :
{"name" : "Homer"
"lastname" : "Simpson"
"age" : 30
}
}
and then, I want to be able to read from the file to extract data from it with something like this:
int main(){
xObject bart;
bart.name = "Bart";
//ACTUAL USE OF THE .JSON FILE HERE
myFile = ("File.json");
bart.lastname = Deserializer(myFile).getLastname(); //It is supossed to assign "Simpson"
//to the lastname reading from the serialized
//homer class file described above.
bart.age = Deserializer(myFile).getAge() - 20; //Sets homer's age minus 20 years.
return 0;
}
So, how can I do that on c++? (Libraries implementation accepted)
And how could I retrieve the class name that has been serialized?
For example Deserialize(myFile).getClassName() should return "homer"
I've done something similar in java with XML serialization, and it was pretty straight forward, but it seems that in C++ this is not very easy to do, and I'm relatively new to C++.

Answer 1

In c++ there is not introspection/reflection, so you can't automatically serialize a class without explicitly write your member variables in your stream. For the same reason, you can't retrieved the class name that have been serialized.
So the solution is to write a function in your class that serializes the member variables you want.
Of course you will not reinvent the wheel to format your file in json. You can use: https://github.com/open-source-parsers/jsoncpp.
For instance you can write:
Json::Value root;
root["homer"]["name"]="Homer";
root["homer"]["lastname"]="Simpson";
//etc
ofstream file;
file.open("File.json");
file << root;
file.close();
However, for the read, you can do as you wanted:
Json::Value root2;
ifstream file2;
file2.open("File.json");
file2 >> root2;
file2.close();
xObject homer;
homer.lastname = root2["homer"]["lastname"].toStyledString();
//etc
Of course your attribute has to be public. Otherwise you need to add a setter function.