reading/writing nested objects

[mohammedalasmar]

Hi,

I've a nested JSON object that I'd like to be able to retrieve and write.

Example:
{ "type":"config-return", "userId":"123456789", "master":{ "configs":{ "mIkjdfuehnduen":{ "dataRate":3333, "fileSize":1000, "fileFormat":"mp4" } } } }

I can easily access userId:
std::string userId = rcvdJSON["userId"];

but how can I access these values dataRate, fileSize and fileFormat? Also, how can I write a JSON object that would look like the example above?

Thanks!
`

[falbrechtskirchinger]

but how can I access these values dataRate, fileSize and fileFormat?

json, the default template instantiation of basic_json, uses the STL comtainers std::map for objects and std::vector for arrays. You can access elements accordingly. For instance:
int dataRate = rcvdJSON["master"]["configs"]["mIkjdfuehnduen"]["dataRate"];

I believe the examples section in the README covers everything you're asking:
https://github.com/nlohmann/json#examples

[mohammedalasmar]

Thanks for your prompt reply!
The examples are very useful but I'm still confused about how to retrieve the data from this JSON object.
In my example above, I need to first read this value:mIkjdfuehnduen (it's unknown to me) then I need to use this value to access the other parameters. This is what I'm trying:

json jObj = rcvdJSON["master"]["configs"];

but then how can I find out this value mIkjdfuehnduen in jObj? also, how can I use std::vector or std::map here?

Many thanks!

[falbrechtskirchinger]

Thanks for your prompt reply! The examples are very useful but I'm still confused about how to retrieve the data from this JSON object. In my example above, I need to first read this value:mIkjdfuehnduen (it's unknown to me) then I need to use this value to access the other parameters. This is what I'm trying:

json jObj = rcvdJSON["master"]["configs"];

but then how can I find out this value mIkjdfuehnduen in jObj?

Well, if jObj.is_object() is true, then you can iterate over its children like this:

for (auto it = jObj.begin(); it != jObj.end(); ++it) {
    // access object keys using it.key() and values using it.value()
    std::cout << "Key: " << it.key() << "\n";
    std::cout << "Value: " << it.value() << "\n";
}

[mohammedalasmar]

Perfect! Many thanks!