multi-level JSON support.

[horntones]

Hi,
I'm using json.hpp in an attempt to create a jason object from a json string. It appears that it only supports single hierarchy json. for example, I'm trying to parse the following:

std::string myString = "{ "Meta Data": { "1. Information": "Intraday (1min) prices and volumes", "2. Symbol" : "MSFT"}, "Time Series (1min)":{"2017-10-09 16:00:00": {"1. open": "76.3300","2. high" : "76.3400","3. low" : "76.2900"},"2017-10-09 15:59:00": {"1. open": "76.3200","2. high" : "76.3350"} }}";

json j = json::parse(myString);

when I print the json, I only get the top keys parsed:
Meta Data : {"1. Information":"Intraday (1min) prices and volumes","2. Symbol":"MSFT"}
Time Series (1min) : {"2017-10-09 15:59:00":{"1. open":"76.3200","2. high":"76.3
350"},"2017-10-09 16:00:00":{"1. open":"76.3300","2. high":"76.3400","3. low":"7
6.2900"}}

Any advise?
thanks!
Mike

[gregmarr]

How are you printing them? Can you also give the exact code you're using to parse? The code above is invalid.

[horntones]

//create string
std::string myString = "{ "Meta Data": { "1. Information": "Intraday (1min) prices and volumes", "2. Symbol" : "MSFT"}, "Time Series (1min)":{"2017-10-09 16:00:00": {"1. open": "76.3300","2. high" : "76.3400","3. low" : "76.2900"},"2017-10-09 15:59:00": {"1. open": "76.3200","2. high" : "76.3350"} }}";
//parse into json
json j = json::parse(myString);
//print json
for (json::iterator it = j.begin(); it != j.end(); ++it) {
std::cout << it.key() << " : " << it.value() << "\n";
}
results in:
Meta Data : {"1. Information":"Intraday (1min) prices and volumes","2. Symbol":"MSFT"}
Time Series (1min) : {"2017-10-09 15:59:00":{"1. open":"76.3200","2. high":"76.3
350"},"2017-10-09 16:00:00":{"1. open":"76.3300","2. high":"76.3400","3. low":"7
6.2900"}}

Thanks for taking the time to look at this!
Mike

[nlohmann]

You are iterating over the top-level object. If you want to iterate the "sub-objects", you need to iterate over it->value().begin(), it->value().end().

Maybe related: https://stackoverflow.com/questions/45934851/c-nlohmann-json-how-to-iterate-find-a-nested-object

[gregmarr]

Your first line of code still won't compile, due to unquoted quotes within the string. Assuming that you're actually properly quoting these, or reading this from a file or something, then the parse looks to be fine, and you just need to handle objects within your loop, as @nlohmann described.

[gregmarr]

When posting code, you should indent all the lines by at least 4 characters, and leave a blank line before and after. This will make github display your code as code, with the proper spacing.

//create string
std::string myString = "{ "Meta Data": { "1. Information": "Intraday (1min) prices and volumes", "2. Symbol" : "MSFT"}, "Time Series (1min)":{"2017-10-09 16:00:00": {"1. open": "76.3300","2. high" : "76.3400","3. low" : "76.2900"},"2017-10-09 15:59:00": {"1. open": "76.3200","2. high" : "76.3350"} }}";
//parse into json
json j = json::parse(myString);
//print json
for (json::iterator it = j.begin(); it != j.end(); ++it) {
    std::cout << it.key() << " : " << it.value() << "\n";
}

[horntones]

Thank you for the tip for posting code. I'm not sure this library is going to work for me as it doesn't readily support nested json. (it->value().begin(), it->value().end() method) does not compile. I'm simply trying to parse out a multi-level json data like the example shown into an array that I can use for analysis and graphing.
any suggestions on methodology (besides writing my own parser) would be appreciated.
thanks again!

[gregmarr]

It supports nested json just fine. Did you read the stackoverflow post above?

[horntones]

I did.
So I tried navigating the hierarchy. As only the top level key pairs are parsed. I tried parsing the value associated with the top key pairs. This would work nicely, however it throws and exception when tying to parse j_meta. Pardon my novice-ness here, I'm a hardware guy that used to write C many moons ago. Just getting back in the swing of things... and how they've changed. :)

	std::string myString = "{ \"Meta Data\": { \"1. Information\": \"Intraday (1min) prices and volumes\", \"2. Symbol\" : \"MSFT\"}, \"Time Series (1min)\":{\"2017-10-09 16:00:00\": {\"1. open\": \"76.3300\",\"2. high\" : \"76.3400\",\"3. low\" : \"76.2900\"},\"2017-10-09 15:59:00\": {\"1. open\": \"76.3200\",\"2. high\" : \"76.3350\"} }}"; 

        json j = json::parse(myString);

	// iterate the array

	for (json::iterator it = j.begin(); it != j.end(); ++it) {
		if (it.key() == "Meta Data") {
			std::cout << "Meta Data Found!\n\t" << it.value() << std::endl;
			//output here is: 
				//Meta Data Found!
				//	{"1. Information":"Intraday (1min) prices and volumes", "2. Symbol" : "MSFT"}
			std::cout << "Parsing Meta Data..." << std::endl;
			json j_meta = json::parse(it.value().get<std::string>());  //Exception Thrown here
			//print the items
			for (json::iterator it_meta = j_meta.begin(); it_meta != j_meta.end(); ++it) {
				std::cout << "\t" << it_meta.key() << "  " << it_meta.value() << std::endl;
			}
		}
		//std::cout << it.key() << std::endl; //: " << it.value() << "\n";
	}

[gregmarr]

It's parsing the entire thing. It may look like it's not because when you write it to cout it dumps it back to a json string. Remove the second json::parse line, and replace j_meta with it.value() in the second for loop and you should get what you want.

[horntones]

That worked! Totally appreciate your help on this!