Compilation errors in ofParameter.h

Hi,

I am trying to run a sample project:
https://github.com/npisanti/ofxPDSP/tree/master/example-midi_polysynth. I used the project generator to create the project for Mac 10.11 but I’ve got the following errors:

	template <typename T>
	struct has_loading_support {
	    static istream & stream;
	    static T & x;
	    static const bool value = sizeof(check(stream >> x)) == sizeof(yes);
                                                         **^ Expected expression**
	};

	template <typename T>
	struct has_saving_support {
	    static ostream & stream;
	    static T & x;
	    static const bool value = sizeof(check(stream << x)) == sizeof(yes);
                                                         **^ Expected expression**
	};

	template <typename T>
	struct has_stream_operators {
	    static const bool can_load = has_loading_support<T>::value;
	    static const bool can_save = has_saving_support<T>::value;
	    static const bool value = can_load && can_save;
	};

template<typename ParameterType>
inline std::string ofParameter<ParameterType>::toString() const{
    try{
        return of::priv::toStringImpl(obj->value);
                  **^^^^^^^^^^^^^^^ No matching function for call to toStringImpl**
    }catch(...){
        ofLogError("ofParameter") << "Trying to serialize non-serializable parameter";
        return "";
    }
}

template<typename ParameterType>
inline void ofParameter<ParameterType>::fromString(const std::string & str){
    try{
        set(of::priv::fromStringImpl<ParameterType>(str));
                  **^^^^^^^^^^^^^^^ No matching function for call to toStringImpl**
    }catch(...){
        ofLogError("ofParameter") << "Trying to de-serialize non-serializable parameter";
    }
}

Any advices on how to solve this would be greatly appreciated!

i’ve updated the example-midi_polysynth and the issue should be solved now, it was fixed by adding

#include "ofMain.h"

to voice.h
(it is a bit strange as i put the necessary ifndef guards to the ofxPDSPParameter class)