multi-level JSON support. #775

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1. gregmarr commented on Oct 10, 2017

   

   gregmarr

   on Oct 10, 2017

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   How are you printing them? Can you also give the exact code you're using to parse? The code above is invalid.
2. horntones commented on Oct 10, 2017

   

   horntones

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   //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
3. nlohmann commented on Oct 10, 2017

   

   nlohmann

   on Oct 10, 2017

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   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
4. gregmarr commented on Oct 10, 2017

   

   gregmarr

   on Oct 10, 2017

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   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.
5. gregmarr commented on Oct 10, 2017

   

   gregmarr

   on Oct 10, 2017

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   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";
   }
   
6. horntones commented on Oct 10, 2017

   

   horntones

   on Oct 10, 2017

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   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!
7. gregmarr commented on Oct 10, 2017

   

   gregmarr

   on Oct 10, 2017

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   It supports nested json just fine. Did you read the stackoverflow post above?
8. horntones commented on Oct 10, 2017

   

   horntones

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   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";
   	}
   
9. gregmarr commented on Oct 10, 2017

   

   gregmarr

   on Oct 10, 2017

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   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.
10. horntones commented on Oct 10, 2017

    

    horntones

    on Oct 10, 2017

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    That worked! Totally appreciate your help on this!

    👍React with 👍2Reacted by Niels Lohmann and chipcraft
11. nlohmann

    added

    solution: proposed fixa fix for the issue has been proposed and waits for confirmationa fix for the issue has been proposed and waits for confirmation

    on Oct 10, 2017
12. horntones

    closed this as completedon Oct 10, 2017