Create a json array in C++

Question

So im trying to create a json Object in c++ dynamically. I want to add a timestamp and then an array with the data included. So thats what my json String would look like : ``` { "timestep": "2160.00", "vehicles": [ { "id": "35092_35092_353", "x": "6.988270", "y": "50.872139", "angle": "-20.812787", "type": "passenger_P_14_1", "speed": "0.000000", "pos": "4.600000", "lane": "4.600000", "slope": "4.600000" }, { "id": "35092_35092_353", "x": "6.988270", "y": "50.872139", "angle": "-20.812787", "type": "passenger_P_14_1", "speed": "0.000000", "pos": "4.600000", "lane": "4.600000", "slope": "4.600000" }, { "id": "35092_35092_353", "x": "6.988270", "y": "50.872139", "angle": "-20.812787", "type": "passenger_P_14_1", "speed": "0.000000", "pos": "4.600000", "lane": "4.600000", "slope": "4.600000" } ] } ``` Im totally new to C++ and im using the Casablanca ( C++ REST SDK) package. So im having a really hard time producing the code. And i cant find any working solutions. I found this on the wik…

Accepted Answer

There are 2 mechanisms. If you are used to std c++ libraries, this should look familiar. Element vector is derived from std::vector.

```
json::value::element_vector e;
// the first item in the pair is the array index, the second the value
e.push_back(std::make_pair(json::value(0), json::value(false)));
e.push_back(std::make_pair(json::value(1), json::value::string(U("hello"))));
json::value arr(e);
```

And, if you prefer a cleaner look, and can accept a less efficient compiled result:

```
json::value arr;
arr[0] = json::value(false);
arr[1] = json::value(U("hello"));
```

From your message you have tried a bunch of stuff. If you have tried mechanisms like these but they didn't work, give us a sample program that demontrates the failure and we'll have a crack at it.

To get the basic structure in your file above:

```
json::value vehicles;
vehicles[0] = // 1st vehicle object
vehicles[1] = // 2nd vehicle object
// etc
json::value root;
root[L"timestep"] = json::number(2160.0);
root[L"vehicles"] = vehicles;
```

Create a json array in C++

Solution

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