JSON for Modern C++  3.7.0

◆ 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>
template<typename KeyT >
iterator nlohmann::basic_json::find ( KeyT &&  key)
inline

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.

Note
This method always returns end() when executed on a JSON type that is not an object.
Parameters
[in]keykey value of the element to search for.
Returns
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.
Complexity
Logarithmic in the size of the JSON object.
Example
The example shows how find() is used.
1 #include <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int main()
7 {
8  // create a JSON object
9  json j_object = {{"one", 1}, {"two", 2}};
10 
11  // call find
12  auto it_two = j_object.find("two");
13  auto it_three = j_object.find("three");
14 
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';
20 }
basic_json<> json
default JSON class
Definition: json.hpp:2355

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
contains(KeyT&&) const – checks whether a key exists
Since
version 1.0.0

Definition at line 18346 of file json.hpp.