nholmann_json_iteration

#include <iostream>
#include <string>
#include <map>
using namespace std;

#include <json.hpp>
using json = nlohmann::json;

int main() {
	json j_currencies = { 
		{"england", {
				    {"name", "euro"},
				    {"value", 57.99}
			    }},
		{"mexico", {
				   {"name", "peso"},
				   {"value", 31.99}
			   }},
		{"us", {
			       {"name", "USD"},
			       {"value", 42.99}
		       }}
	};

	struct currency {
		std::string country{};
		std::string name{};
		unsigned int value{};
	};

	map <string, currency> currencies;
	for ( auto iter = j_currencies.begin(); iter != j_currencies.end(); ++iter ) {
		cout << iter.key() << endl;
		cout << iter.value() << endl;
		cout << iter->get<string>() << endl;
	}
}

shell_output

➜  json_test  g++ --std=c++11 main.cpp -o main.exe && ./main.exe                                                                                                                                        <<<
main.cpp:33:16: error: no member named 'key' in 'nlohmann::basic_json<std::map, std::vector, std::__1::basic_string<char>, bool, long long, double, std::allocator>::iterator'
                cout << iter.key() << endl;
                        ~~~~ ^
main.cpp:34:16: error: no member named 'value' in 'nlohmann::basic_json<std::map, std::vector, std::__1::basic_string<char>, bool, long long, double, std::allocator>::iterator'
                cout << iter.value() << endl;
                        ~~~~ ^
2 errors generated.

The key() and value() functions are no longer supported, because they are nonstandard and broke the reverse iterators.

However, without lines 33 and 34 I get the following runtime error:

libc++abi.dylib: terminating with uncaught exception of type std::logic_error: cannot cast object to NSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEE
Abort trap: 6

This should work:

for ( auto iter = j_currencies.begin(); iter != j_currencies.end(); ++iter ) {
    cout << *iter << endl;
}