How do I traverse a json object and add new elements into the hierarchy

[michael-a-green]

** - Describe what you want to achieve. **

I want to generate a JSON object that has hierarchy. Something like this:

{
    "mything": "simple_thing",
    "thing_projects": {
        "name": "Project A",
        "revisions": [
            {
                "revision":1,
                "name":"particular_thing"
                "children":[{"name":"part1_of_particular_thing"},{"name":"part2_of_particular_thing"}]
            },
            {
                "revision" : 22
            }
        ]
    }
}

I want to create this on the fly as I'm traversing another data structure. But I don't know how to traverse to arbitrary locations in a json object.

** - Describe what you tried. **

I've tried this:

json::iterator it;
  for (it = (*userdata_jptr).begin(); it != (*userdata_jptr).end(); ++it){

    if (it.key() == "name" && it.value() == "Project A") {
      break;
    }
  }

  it["name"] = temp_scope_name;
  it["scope_type"] = temp_scopetype_name;

where userdata_jptr is a pointer to the json object I'm trying to construct.

But when I try to compile this code I get errors like this:

src/main.cpp: In function ‘void myScope(ucisT, ucisScopeT, json*, int)’:
/src/main.cpp:375:6: error: invalid conversion from ‘const char*’ to ‘nlohmann::detail::iter_impl<nlohmann::basic_json<> >::difference_type’ {aka ‘long int’} [-fpermissive]
  375 |   it["name"] = temp_scope_name;
      |      ^~~~~~
      |      |
      |      const char*
In file included from src/main.cpp:27:

What is the right iterator type to use when I want something that will point to the location in the json object to which I want to make changes (just adding things at this point).

Or in general what is the right method to traverse to a certain location in a json object, and then use whatever mechanism was used to iterate to that location and make in-place changes?

** - Describe which system (OS, compiler) you are using. **

Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/9/lto-wrapper
OFFLOAD_TARGET_NAMES=hsa:nvptx-none
Target: x86_64-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info --mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64 --enable-languages=c,c++,objc,fortran,obj-c++,ada,go,d --enable-offload-targets=hsa,nvptx-none=/usr/nvptx-none, --without-cuda-driver --disable-werror --with-gxx-include-dir=/usr/include/c++/9 --enable-ssp --disable-libssp --disable-libvtv --disable-cet --disable-libcc1 --enable-plugin --with-bugurl=https://bugs.opensuse.org/ --with-pkgversion='SUSE Linux' --with-slibdir=/lib64 --with-system-zlib --enable-libstdcxx-allocator=new --disable-libstdcxx-pch --enable-libphobos --enable-version-specific-runtime-libs --with-gcc-major-version-only --enable-linker-build-id --enable-linux-futex --enable-gnu-indirect-function --program-suffix=-9 --without-system-libunwind --enable-multilib --with-arch-32=x86-64 --with-tune=generic --with-build-config=bootstrap-lto-lean --enable-link-mutex --build=x86_64-suse-linux --host=x86_64-suse-linux
Thread model: posix
gcc version 9.2.1 20190820 [gcc-9-branch revision 274748] (SUSE Linux) 

LSB Version:	n/a
Distributor ID:	openSUSE
Description:	openSUSE Tumbleweed
Release:	20190921
Codename:	n/a

Linux <machine name> 5.2.14-1-default #1 SMP Tue Sep 10 10:52:01 UTC 2019 (374b0ae) x86_64 x86_64 x86_64 GNU/Linux

• Describe which version of the library you are using (release version, develop branch).

Version 3.7.0.1-1

Thanks

[nlohmann]

The error message looks like as if you would like to access an array (only integer indices are allowed) with a key. The latter is only allowed for objects.

[michael-a-green]

The error message looks like as if you would like to access an array (only integer indices are allowed) with a key. The latter is only allowed for objects.

Thanks for the response. How should I do it?

[psotos]

I would also like to know the answer to this. Thanks!

[nlohmann]

This is hard to answer in general. Can you provide a small example?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.