JSON for Modern C++ 3.10.4

◆ find() [1/2]

template<template< typename U, typename V, typename... Args > class ObjectType = std::map, template< typename U, typename... Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer, class BinaryType = std::vector<std::uint8_t>>
template<typename KeyT >
iterator nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::find ( KeyT &&  key)

Finds an element in a JSON object with key equivalent to key. If the element is not found or the JSON value is not an object, end() is returned.

This method always returns end() when executed on a JSON type that is not an object.
[in]keykey value of the element to search for.
Iterator to an element with key equivalent to key. If no such element is found or the JSON value is not an object, past-the-end (see end()) iterator is returned.
Logarithmic in the size of the JSON object.
The example shows how find() is used.
1#include <iostream>
2#include <nlohmann/json.hpp>
4using json = nlohmann::json;
6int main()
8 // create a JSON object
9 json j_object = {{"one", 1}, {"two", 2}};
11 // call find
12 auto it_two = j_object.find("two");
13 auto it_three = j_object.find("three");
15 // print values
16 std::cout << std::boolalpha;
17 std::cout << "\"two\" was found: " << (it_two != j_object.end()) << '\n';
18 std::cout << "value at key \"two\": " << *it_two << '\n';
19 std::cout << "\"three\" was found: " << (it_three != j_object.end()) << '\n';
basic_json<> json
default JSON class
Definition: json.hpp:3472

Output (play with this example online):
"two" was found: true
value at key "two": 2
"three" was found: false
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/find__key_type.cpp -o find__key_type 
See also
see contains(KeyT&&) const – checks whether a key exists
version 1.0.0

Definition at line 22037 of file json.hpp.