Error when trying to parse a JSON array

[m4l490n]

I'm trying to parse a JSON array with the following code:

static void from_json(const nlohmann::json& j, wbid::MultiIO &multiIO);

int main()
{
    /* Some code before */

    for(wbid::MultiIO multiIO : parsedJsonForWBID["io"])
    {
        first_entry[i++] = multiIO;
    }

    /* Some code after */
}

static void from_json(const nlohmann::json& j, wbid::MultiIO &multiIO)
{
    wbid::MultiIOColor color;
    j.at("color").get_to(color);
    multiIO.setColor(color);

    wbid::MultiIOType type;
    j.at("type").get_to(type);
    multiIO.setType(type);

    uint16_t value;
    j.at("color").get_to(value);
    multiIO.setValue(value);
}

And I'm getting the following error and warning:

make all 
Building file: ../src/main.cpp
Invoking: GCC C++ Compiler
g++ -std=c++2a -I../src -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/main.d" -MT"src/main.o" -o "src/main.o" "../src/main.cpp"
../src/main.cpp: In function ‘int main(int, char**)’:
../src/main.cpp:120:59: error: conversion from ‘nlohmann::basic_json<>’ to non-scalar type ‘wbid::MultiIO’ requested
  120 |         for(wbid::MultiIO multiIO : parsedJsonForWBID["io"])
      |                                                           ^
../src/main.cpp: At global scope:
../src/main.cpp:204:13: warning: ‘void from_json(const json&, wbid::MultiIO&)’ defined but not used [-Wunused-function]
  204 | static void from_json(const nlohmann::json& j, wbid::MultiIO &multiIO)
      |             ^~~~~~~~~
make: *** [src/subdir.mk:29: src/main.o] Error 1
"make all" terminated with exit code 2. Build might be incomplete.

But I don't know why if I'm doing exactly as I'm doing on another program. The only difference is that I'm using a struct in the other program that works instead of a class (wbid::MultiIO) I'm using here. Is there something different to do when using a class?

[nlohmann]

You need to define the from_json function in the namespace of the respective type. So please try:

namespace wbid {
void from_json(const nlohmann::json& j,MultiIO &multiIO)
{
    wbid::MultiIOColor color;
    j.at("color").get_to(color);
    multiIO.setColor(color);

    wbid::MultiIOType type;
    j.at("type").get_to(type);
    multiIO.setType(type);

    uint16_t value;
    j.at("color").get_to(value);
    multiIO.setValue(value);
}
}

Also make sure you have conversion functions for all the other types such as wbid::MultiIOColor or wbid::MultiIOType.

[m4l490n]

Awesome! that was it! I just needed to put the from_json in the same namespace. Thanks!!