Sans Pareil Technologies, Inc.

Key To Your Business

JSON API



A simple API for reading/writing JSON data using C++11. No runtime dependencies other than C++11. The standard JSON value types are represented as the appropriate instances of Value. Value instance are non-copyable and hence the API cannot be packaged as a Windows DLL. On Windows, we include the sources directly into the target project.

Reading

Reading JSON data is accomplished using the convenience read or fromFile functions defined in the spt::json::io namespace. These functions conveniently wrap the implementations in the Reader class hierarchy. Reader functions return an instance of Value::Ptr which will need to be extracted into either an Object or Array instance.

#include <spt/json/Object.h>
#include <spt/json/Array.h>
#include <spt/json/io/Reader.h>

  using spt::json::Array;
  using spt::json::Object;
  using spt::json::Value;

  std::istream istream; // initialised to some valid stream
  Value::Ptr ptr = spt::json::io::read( istream );

  if ( ptr->getType() == Value::Type::Object )
  {
    const Object* obj = static_cast<const Object*>( ptr.get() );
    double dval = obj->getValue<double>( "doubleValue" );
    const std::string& str = obj->get<std::string>( "stringValue" );
    bool bval = obj->getValue<bool>( "boolValue" );
  }
  else if ( ptr->getType() == Value::Type::Array )
  {
    const Array* arr = static_cast<const Array*>( ptr.get() );
    double dval = arr->getValue<double>( 0 );
    const std::string& str = arr->get<std::string>( 1 );
    bool bval = arr->getValue<bool>( 2 );
  }



Writing

Writing JSON object model (intances of Object or Array) is accomplished through the toFile functions in the spt::json::io namespace or using the Json::toJson function. All output implementations use the Writer class hierarchy for producing the output.

#include <spt/json/Object.h>
#include <spt/json/Array.h>
#include <spt/json/String.h>
#include <spt/json/Number.h>


  using spt::json::Array;
  using spt::json::Object;
  using spt::json::Value;
  using spt::json::String;
  using spt::json::Number;

  Object object;
  object += Object::Pair( "one", Value::Ptr( new String( "one" ) ) );
  object += Object::Pair( "two", Value::Ptr( new Number( static_cast<int64_t>( 2 ) ) ) );

  std::ostream ostream; // initialised to some valid stream
  object.toJson( ostream, false );

  Array arr;
  arr += Value::Ptr( new String( "one" ) );
  arr += Value::Ptr( new Number( 4.4 ) );
  object.toJson( ostream, true );