Parsing JSON with boost property tree

Question

I'm building an application that gets movie information from themoviedb.com. The information is provided in a JSON file. I'm trying to store the information using boost property tree. But There is a little problem.

I illustrate the problem by the following code:

#include <vector> #include <boost/property_tree/ptree.hpp> #include <boost/property_tree/json_parser.hpp> #include <boost/foreach.hpp> using namespace std; using boost::property_tree::ptree; class single_t{ int sID; string sName; public: void setID(int ID){sID=ID;} int getID(){return sID;} void setName(string Name){sName=Name;} string getName(){return sName;} }; typedef vector<single_t*> multiple_t; class foo{ string fTitle; multiple_t fItems; public: string getTitle(){return fTitle;} void setTitle(string Title){fTitle=Title;} multiple_t getItems(){return fItems;} void setItems(multiple_t Items){fItems = Items;} void setItems(single_t Item){fItems.push_back(&Item);} }; int main () { try{ string response = "{\"title\":\"Foo\",\"items\":[{\"id\":123,\"name\":\"test1\"},{\"id\":456,\"name\":\"test2\"}]}"; ptree pt; stringstream ss; ss << response; read_json(ss, pt); foo results; results.setTitle(pt.get<string>("title")); BOOST_FOREACH(ptree::value_type &v,pt.get_child("items")){ single_t result; result.setID(v.second.get<int>("id")); result.setName(v.second.get<string>("name")); results.setItems(result); } cout << "Tilte: " << results.getTitle() << endl; cout << "Items:" << endl; for (int i=0; i!=results.getItems().size(); i++) { cout << "\tID: " << results.getItems()[i]->getID()<< endl; cout << "\tName: " << results.getItems()[i]->getName()<< endl; } } catch (exception& e) { cout << "Exception: " << e.what(); } }

But when I run this I get the following output:

Tilte: Foo Items: ID: 456 Name: test2 ID: 456 Name: test2

Does anyone know what I'm doing wrong? I guess it is in the BOOST_FOREACH code.

PS: Using Xcode 4.5.2 with LLVM GCC 4.2 Compiler.

ForEveR · Accepted Answer · 2012-12-20 12:48:23Z

5

Problem is not with property_tree, problem is, that you try store pointer to local variable in vector. You can save by value, or use some smart pointer (for example boost::shared_ptr).

Problem:

void setItems(single_t Item){fItems.push_back(&Item);}

After exit from this function, local variable Item will be destroyed, so you have dangling pointer.

edited Dec 20, 2012 at 12:48

answered Dec 20, 2012 at 12:35

ForEveR

56.1k2 gold badges127 silver badges139 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Glenn Vonk Over a year ago

Thank you for the quick response, I'm fairly new to c++ coding, so could you help me solve this?

Glenn Vonk Over a year ago

I have a fix. I changed: typedef vector<single_t*> multiple_t; to typedef vector<single_t> multiple_t;, and changed the rest of the code accordingly. Are there any disadvantages to this method?

ForEveR Over a year ago

@GlennVonk No, in your case there is no disadvantages.

Collectives™ on Stack Overflow

Parsing JSON with boost property tree

1 Answer 1

3 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Linked

Related