newbie usage question

Hello,

I was looking over your json framework and think that it is exactly what I need for my project, but in your documentation I did not see how to iterate over a json set of attributes.

For example if I have a json file that looks like this:

{
    "answers": [],
    "corrections": [],
    "infoboxes": [
        {
            "content": "...",
            "engine": "...",
            "id": "...",
            "img_src": "...",
            "infobox": "...",
            "urls": [
                {
                    "title": "...",
                    "url": "..."
                }
            ]
        }
    ],
    "number_of_results": ...,
    "query": "...",
    "results": [
        {
            "category": "....",
            "content": "...",
        },
        {
            "category": "....",
            "content": "...",
        },
        {
            "category": "....",
            "content": "...",
        },
        {
            "category": "....",
            "content": "...",
        },
        {
            "category": "....",
            "content": "...",
        }
    ],
    "suggestions": [],
    "somehting": [
        [
            "one",
            "two"
        ]
    ]
}

Then I have to 2 possible needs.

1. I would read it in a string variable and want to iterate over the "category" and "content" attributes to collect all of the different information.

2. I would like to be able to create the above json using your reference method.

In your example I would like to create:

{
  "pi": 3.141,
  "happy": true,
  "name": "Niels",
  "nothing": null,
  "answer": {
    "everything": 42
  },
  "list": [1, 0, 2],
  "object": {
    "currency": "USD",
    "value": 42.99
  },
  "object": {
    "currency": "USD",
    "value": 2.99
  },
  "object": {
    "currency": "USD",
    "value": 4.99
  }
}

You show:

// add another object (using an initializer list of pairs)
j["object"] = { {"currency", "USD"}, {"value", 42.99} };

but can it also be done something like:

// add another object (using an initializer list of pairs)
j["object"] ["currency"]=  "USD"
j["object"]["value"]= 42.99;

but that would only be for 1 object and I need to be able to add many "object" items to a structure.

I also need to be able to reference nested items in a similar way if possible.

Thanks,

[nlohmann]

You cannot create a JSON like

{
  "pi": 3.141,
  "happy": true,
  "name": "Niels",
  "nothing": null,
  "answer": {
    "everything": 42
  },
  "list": [1, 0, 2],
  "object": {
    "currency": "USD",
    "value": 42.99
  },
  "object": {
    "currency": "USD",
    "value": 2.99
  },
  "object": {
    "currency": "USD",
    "value": 4.99
  }
}

because each key in an object must be unique. See also https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a5e48a7893520e1314bf0c9723e26ea2a.html#a5e48a7893520e1314bf0c9723e26ea2a (section "Behavior").

You could instead create an array of objects, e.g.

[
{
    "currency": "USD",
    "value": 4.99
},
{
    "currency": "USD",
    "value": 2.99
}
]

Hello, What I have is a server returning some json with the following structure: { "answers": [], "corrections": [], "infoboxes": [ { "content": "...", "engine": "...", "id": "...", "img_src": "...", "infobox": "...", "urls": [ { "title": "...", "url": "..." } ] } ], "number_of_results": 000, "query": "...", "results": [ { "category": "...", "content": "...", "engine": "...", "engines": [ "1", "2", "3" ], "positions": [ 1, 2, 1 ], "score": 7.5, "title": "...", "url": "..." }, { "category": "...", "content": "...", "engine": "...", "engines": [ "1", "2", "3" ], "positions": [ 1, 2, 1 ], "score": 7.5, "title": "...", "url": "..." }, { "category": "...", "content": "...", "engine": "...", "engines": [ "1", "2", "3" ], "positions": [ 1, 2, 1 ], "score": 7.5, "title": "...", "url": "..." } ], "suggestions": [], "unresponsive_engines": [ [ "A", "B" ], [ "ONE", "TWO" ] ] } And I am trying to find a way to read the data that is in each "category", "content", "engine", "engines", "positions", etc.... as these are an array of objects of the type: { "category": "...", "content": "...", "engine": "...", "engines": [ "1", "2", "3" ], "positions": [ 1, 2, 1 ], "score": 7.5, "title": "...", "url": "..." } Any ideas on this as this is the structure that the server is returning to me in the call? Thanks again

…

On Mon, Apr 23, 2018 at 2:48 AM, Niels Lohmann ***@***.***> wrote: You cannot create a JSON like { "pi": 3.141, "happy": true, "name": "Niels", "nothing": null, "answer": { "everything": 42 }, "list": [1, 0, 2], "object": { "currency": "USD", "value": 42.99 }, "object": { "currency": "USD", "value": 2.99 }, "object": { "currency": "USD", "value": 4.99 } } because each key in an object must be unique. See also https://nlohmann.github.io/json/classnlohmann_1_1basic__json_ a5e48a7893520e1314bf0c9723e26ea2a.html#a5e48a7893520e1314bf0c9723e26ea2a (section "Behavior"). You could instead create an array of objects, e.g. [ { "currency": "USD", "value": 4.99 }, { "currency": "USD", "value": 2.99 } ] — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1063 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AXkxHgcjbieKNRZd_WjRsSvFV3QzhJceks5trXlWgaJpZM4Te8ke> .

[nlohmann]

You would use the operator[] in most cases, as described in https://github.com/nlohmann/json#json-as-first-class-data-type. Iteration is done similar to any other STL container.

Thanks for the information and I will work on it. Is there, by chance any examples for this? My json data feed is received into an stl std::string or std::streamstring type and I am mostly just looking to iterate through the array of objects to get the list of items. Thanks again,

…

On Mon, Apr 23, 2018 at 7:57 AM, Niels Lohmann ***@***.***> wrote: You would use the operator[] in most cases, as described in https://github.com/nlohmann/json#json-as-first-class-data-type. Iteration is done similar to any other STL container. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1063 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AXkxHkpTuou2IKgoCvG6JjRL5YjjamOxks5trcGSgaJpZM4Te8ke> .

[nlohmann]

You can see examples here: https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a233b02b0839ef798942dd46157cc0fe6.html#a233b02b0839ef798942dd46157cc0fe6

[nlohmann]

Do you need further assistance?

Hi Niels, I think that I am all set for the moment. We can close this ticket. Thanks again,

…

On Wed, Apr 25, 2018 at 4:42 PM, Niels Lohmann ***@***.***> wrote: Do you need further assistance? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1063 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AXkxHo1uRtQHM9oSBkRX8ccgXxIY9dDSks5tsN-9gaJpZM4Te8ke> .