Using QString as string type

[mlutken]

Hi

It would be very nice if one could do:
using json = nlohmann::basic_json < std::map, std::vector, QString >;

And have everything work.
Right now it seems stringstream are used to stringify etc... So it does not quite compile.

Otherwise I am pretty impressed by the way this library works. Having used hson mostly from PHP, where it's very simple, this is clearly the way to go in C++ :)

-Martin

[nlohmann]

Could you please paste the compiler error you got when trying to use QString as string type?

[mlutken]

I will be happy too :)

This is a minimal example:

#include <QString>
#include "json.hpp"

//using json = nlohmann::basic_json<std::map, std::vector, std::string>;
using json = nlohmann::basic_json<std::map, std::vector, QString>;

int main()
{
    json j;
    j["attrib1"] = "val1";

    return 0;
}

I get this from gcc:
In file included from ../qjson-test/main.cc:3:0:
../qjson-test/json.hpp: In instantiation of 'nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type& nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::operator [with T = const char; ObjectType = std::map; ArrayType = std::vector; StringType = QString; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::reference = nlohmann::basic_json<std::map, std::vector, QString>&; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type = nlohmann::basic_json<std::map, std::vector, QString>]':
../qjson-test/main.cc:11:16: required from here
../qjson-test/json.hpp:3487:80: error: no matching function for call to 'std::domain_error::domain_error(const QString)'
throw std::domain_error("cannot use operator[] with " + type_name());
^
In file included from /usr/include/c++/5.3.1/system_error:41:0,
from /usr/include/c++/5.3.1/bits/ios_base.h:46,
from /usr/include/c++/5.3.1/ios:42,
from /usr/include/c++/5.3.1/ostream:38,
from /usr/include/c++/5.3.1/iterator:64,
from ../../../../Qt/5.6/gcc_64/include/QtCore/qbytearray.h:46,
from ../../../../Qt/5.6/gcc_64/include/QtCore/qstring.h:42,
from ../../../../Qt/5.6/gcc_64/include/QtCore/QString:1,
from ../qjson-test/main.cc:2:
/usr/include/c++/5.3.1/stdexcept:147:14: note: candidate: std::domain_error::domain_error(const char_)
explicit domain_error(const char_);
^
/usr/include/c++/5.3.1/stdexcept:147:14: note: no known conversion for argument 1 from 'const QString' to 'const char_'
/usr/include/c++/5.3.1/stdexcept:145:14: note: candidate: std::domain_error::domain_error(const string&)
explicit domain_error(const string& __arg);
^
/usr/include/c++/5.3.1/stdexcept:145:14: note: no known conversion for argument 1 from 'const QString' to 'const string& {aka const std::__cxx11::basic_string&}'
/usr/include/c++/5.3.1/stdexcept:142:9: note: candidate: std::domain_error::domain_error(const std::domain_error&)
class domain_error : public logic_error
^
/usr/include/c++/5.3.1/stdexcept:142:9: note: no known conversion for argument 1 from 'const QString' to 'const std::domain_error&'
In file included from ../qjson-test/main.cc:3:0:
../qjson-test/json.hpp: In member function 'nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type& nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::operator [with T = const char; ObjectType = std::map; ArrayType = std::vector; StringType = QString; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::reference = nlohmann::basic_json<std::map, std::vector, QString>&; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type = nlohmann::basic_json<std::map, std::vector, QString>]':
../qjson-test/json.hpp:3489:5: warning: control reaches end of non-void function [-Wreturn-type]
}
^
Makefile:575: recipe for target 'main.o' failed
make: *_* [main.o] Error 1
14:02:22: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project qjson-test (kit: Desktop Qt 5.6.0 GCC 64bit)
When executing step "Make"
14:02:22: Elapsed time: 00:02.

[gregmarr]

    string_t type_name() const noexcept

Since this is a private function that is only used with the std::domain_error() constructor, changing the return type of this function to std::string should be fine. Can you try that and see if there are any other errors?

[nlohmann]

@gregmarr How comes that you are always that fast ;)

[gregmarr]

@nlohmann I'm not sure this function can really be noexcept, since it creates a string object, which may need to allocate memory.

[mlutken]

I will try and see if that helps :-)

[mlutken]

I does help.
Have some trouble with dump(), but will try and explore a little more first :)

[mlutken]

Ok, some is working but this program using dump() gives a lot of compiler errors:

using json = nlohmann::basic_json<std::map, std::vector, QString>;

using namespace std;

int main()
{
    json j;
    j["attrib1"] = "val1";
    auto s = j.dump(4);
    return 0;
}

[mlutken]

Errors here:

g++ -c -pipe -g -std=gnu++0x -Wall -W -D_REENTRANT -fPIC -DQT_QML_DEBUG -DQT_CORE_LIB -I../qjson-test -I. -I../../../../Qt/5.6/gcc_64/include -I../../../../Qt/5.6/gcc_64/include/QtCore -I. -I../../../../Qt/5.6/gcc_64/mkspecs/linux-g++ -o main.o ../qjson-test/main.cc
In file included from ../qjson-test/main.cc:4:0:
../qjson-test/json.hpp: In instantiation of 'nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::string_t nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::dump(int) const [with ObjectType = std::map; ArrayType = std::vector; StringType = QString; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::string_t = QString]':
../qjson-test/main.cc:15:22:   required from here
../qjson-test/json.hpp:2110:23: error: could not convert 'std::__cxx11::basic_stringstream<_CharT, _Traits, _Alloc>::str() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::__cxx11::basic_stringstream<_CharT, _Traits, _Alloc>::__string_type = std::__cxx11::basic_string<char>]()' from 'std::__cxx11::basic_stringstream<char>::__string_type {aka std::__cxx11::basic_string<char>}' to 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}'
        return ss.str();
                    ^
../qjson-test/json.hpp: In instantiation of 'void nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::dump(std::ostream&, bool, unsigned int, unsigned int) const [with ObjectType = std::map; ArrayType = std::vector; StringType = QString; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; std::ostream = std::basic_ostream<char>]':
../qjson-test/json.hpp:2103:17:   required from 'nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::string_t nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::dump(int) const [with ObjectType = std::map; ArrayType = std::vector; StringType = QString; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::string_t = QString]'
../qjson-test/main.cc:15:22:   required from here
../qjson-test/json.hpp:6035:23: error: no match for 'operator<<' (operand types are 'std::ostream {aka std::basic_ostream<char>}' and 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}')
                    o << string_t(new_indent, ' ') << "\""
                    ^
In file included from /usr/include/c++/5/iostream:39:0,
                from ../qjson-test/main.cc:2:
/usr/include/c++/5/ostream:108:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ostream_type& (*)(std::basic_ostream<_CharT, _Traits>::__ostream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(__ostream_type& (*__pf)(__ostream_type&))
    ^
/usr/include/c++/5/ostream:108:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'std::basic_ostream<char>::__ostream_type& (*)(std::basic_ostream<char>::__ostream_type&) {aka std::basic_ostream<char>& (*)(std::basic_ostream<char>&)}'
/usr/include/c++/5/ostream:117:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ios_type& (*)(std::basic_ostream<_CharT, _Traits>::__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>; std::basic_ostream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
    operator<<(__ios_type& (*__pf)(__ios_type&))
    ^
/usr/include/c++/5/ostream:117:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'std::basic_ostream<char>::__ios_type& (*)(std::basic_ostream<char>::__ios_type&) {aka std::basic_ios<char>& (*)(std::basic_ios<char>&)}'
/usr/include/c++/5/ostream:127:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(ios_base& (*__pf) (ios_base&))
    ^
/usr/include/c++/5/ostream:127:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'std::ios_base& (*)(std::ios_base&)'
/usr/include/c++/5/ostream:166:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(long __n)
    ^
/usr/include/c++/5/ostream:166:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'long int'
/usr/include/c++/5/ostream:170:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(unsigned long __n)
    ^
/usr/include/c++/5/ostream:170:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'long unsigned int'
/usr/include/c++/5/ostream:174:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(bool __n)
    ^
/usr/include/c++/5/ostream:174:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'bool'
In file included from /usr/include/c++/5/ostream:638:0,
                from /usr/include/c++/5/iostream:39,
                from ../qjson-test/main.cc:2:
/usr/include/c++/5/bits/ostream.tcc:91:5: note: candidate: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char; _Traits = std::char_traits<char>]
    basic_ostream<_CharT, _Traits>::
    ^
/usr/include/c++/5/bits/ostream.tcc:91:5: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'short int'
In file included from /usr/include/c++/5/iostream:39:0,
                from ../qjson-test/main.cc:2:
/usr/include/c++/5/ostream:181:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(unsigned short __n)
    ^
/usr/include/c++/5/ostream:181:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'short unsigned int'
In file included from /usr/include/c++/5/ostream:638:0,
                from /usr/include/c++/5/iostream:39,
                from ../qjson-test/main.cc:2:
/usr/include/c++/5/bits/ostream.tcc:105:5: note: candidate: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char; _Traits = std::char_traits<char>]
    basic_ostream<_CharT, _Traits>::
    ^
/usr/include/c++/5/bits/ostream.tcc:105:5: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'int'
In file included from /usr/include/c++/5/iostream:39:0,
                from ../qjson-test/main.cc:2:
/usr/include/c++/5/ostream:192:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(unsigned int __n)
    ^
/usr/include/c++/5/ostream:192:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'unsigned int'
/usr/include/c++/5/ostream:201:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(long long __n)
    ^
/usr/include/c++/5/ostream:201:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'long long int'
/usr/include/c++/5/ostream:205:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(unsigned long long __n)
    ^
/usr/include/c++/5/ostream:205:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'long long unsigned int'
/usr/include/c++/5/ostream:220:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(double __f)
    ^
/usr/include/c++/5/ostream:220:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'double'
/usr/include/c++/5/ostream:224:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(float __f)
    ^
/usr/include/c++/5/ostream:224:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'float'
/usr/include/c++/5/ostream:232:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(long double __f)
    ^
/usr/include/c++/5/ostream:232:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'long double'
/usr/include/c++/5/ostream:245:7: note: candidate: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
    operator<<(const void* __p)
    ^
/usr/include/c++/5/ostream:245:7: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'const void*'
In file included from /usr/include/c++/5/ostream:638:0,
                from /usr/include/c++/5/iostream:39,
                from ../qjson-test/main.cc:2:
/usr/include/c++/5/bits/ostream.tcc:119:5: note: candidate: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
    basic_ostream<_CharT, _Traits>::
    ^
/usr/include/c++/5/bits/ostream.tcc:119:5: note:   no known conversion for argument 1 from 'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' to 'std::basic_ostream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}'
In file included from /usr/include/c++/5/memory:82:0,
                from ../qjson-test/json.hpp:48,
                from ../qjson-test/main.cc:4:
/usr/include/c++/5/bits/shared_ptr.h:66:5: note: candidate: template<class _Ch, class _Tr, class _Tp, __gnu_cxx::_Lock_policy _Lp> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::__shared_ptr<_Tp, _Lp>&)
    operator<<(std::basic_ostream<_Ch, _Tr>& __os,
    ^
/usr/include/c++/5/bits/shared_ptr.h:66:5: note:   template argument deduction/substitution failed:
In file included from ../qjson-test/main.cc:4:0:
../qjson-test/json.hpp:6035:23: note:   'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' is not derived from 'const std::__shared_ptr<_Tp, _Lp>'
                    o << string_t(new_indent, ' ') << "\""
                    ^

I

..... lots an lots ... more errors ...

In file included from ../qjson-test/main.cc:4:0:
../qjson-test/json.hpp:6095:19: note:   'nlohmann::basic_json<std::map, std::vector, QString>::string_t {aka QString}' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>'
                o << string_t("\"") << escape_string(*m_value.string) << "\"";
                ^
In file included from ../../../../Qt/5.6/gcc_64/include/QtCore/QString:1:0,
                from ../qjson-test/main.cc:3:
../../../../Qt/5.6/gcc_64/include/QtCore/qstring.h:1338:28: note: candidate: QDataStream& operator<<(QDataStream&, const QString&)
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QString &);
                            ^
../../../../Qt/5.6/gcc_64/include/QtCore/qstring.h:1338:28: note:   no known conversion for argument 1 from 'std::ostream {aka std::basic_ostream<char>}' to 'QDataStream&'
In file included from ../../../../Qt/5.6/gcc_64/include/QtCore/qstring.h:42:0,
                from ../../../../Qt/5.6/gcc_64/include/QtCore/QString:1,
                from ../qjson-test/main.cc:3:
../../../../Qt/5.6/gcc_64/include/QtCore/qbytearray.h:668:28: note: candidate: QDataStream& operator<<(QDataStream&, const QByteArray&)
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QByteArray &);
                            ^
../../../../Qt/5.6/gcc_64/include/QtCore/qbytearray.h:668:28: note:   no known conversion for argument 1 from 'std::ostream {aka std::basic_ostream<char>}' to 'QDataStream&'
In file included from ../../../../Qt/5.6/gcc_64/include/QtCore/qstring.h:41:0,
                from ../../../../Qt/5.6/gcc_64/include/QtCore/QString:1,
                from ../qjson-test/main.cc:3:
../../../../Qt/5.6/gcc_64/include/QtCore/qchar.h:576:28: note: candidate: QDataStream& operator<<(QDataStream&, QChar)
Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, QChar);
                            ^
../../../../Qt/5.6/gcc_64/include/QtCore/qchar.h:576:28: note:   no known conversion for argument 1 from 'std::ostream {aka std::basic_ostream<char>}' to 'QDataStream&'
make: *** [main.o] Error 1
12:46:19: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project qjson-test (kit: Desktop Qt 5.6.0 GCC 64bit)

[nlohmann]

The first error is related to #268: It is implicitly assumed that std::stringstream::str() would return string_t (which is wrong, it's std::string).

Could you try to replace line 2099 with

std::basic_stringstream<typename string_t::value_type,
                        typename string_t::traits_type,
                        typename string_t::allocator_type> ss;

?

[mlutken]

I wll try :)

[mlutken]

Hi have been on holiday, but will get back to this problem and try you suggestion.
In fact I convenced one of my coworkers that we should push for using this project at our work too. Currently we use picojson.

[mlutken]

Now it complains that QString does not have a traits_type nested type:
5.6/gcc_64/include/QtCore -I. -I../../../../Qt/5.6/gcc_64/mkspecs/linux-g++ -o main.o ../qjson-test/main.cc
In file included from ../qjson-test/main.cc:4:0:
../qjson-test/json.hpp: In instantiation of 'nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::string_t nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::dump(int) const [with ObjectType = std::map; ArrayType = std::vector; StringType = QString; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::string_t = QString]':
../qjson-test/main.cc:15:22: required from here
../qjson-test/json.hpp:2102:68: error: no type named 'traits_type' in 'class QString'
typename string_t::allocator_type> ss;
^
../qjson-test/json.hpp:2102:68: error: no type named 'traits_type' in 'class QString'

[nlohmann]

It seems as if typename string_t::traits_type is not available if string_t is of type QString. I do no know whether it is possible to create suitable string stream for QStrings.

I thought about changing the dump functions return value to std::string, but this would also not help, because there is no implicit conversion from QString to std::string. I am currently clueless whether this combination can work.