JSON for Modern C++  3.7.0

◆ begin() [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>
iterator nlohmann::basic_json::begin ( )
inlinenoexcept

Returns an iterator to the first element.

range-begin-end.svg
Illustration from cppreference.com
Returns
iterator to the first element
Complexity
Constant.
Requirements
This function helps basic_json satisfying the Container requirements:
  • The complexity is constant.
Example
The following code shows an example for begin().
1 #include <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int main()
7 {
8  // create an array value
9  json array = {1, 2, 3, 4, 5};
10 
11  // get am iterator to the first element
12  json::iterator it = array.begin();
13 
14  // serialize the element that the iterator points to
15  std::cout << *it << '\n';
16 }
iter_impl< basic_json > iterator
an iterator for a basic_json container
Definition: json.hpp:14683
iterator begin() noexcept
returns an iterator to the first element
Definition: json.hpp:18500
basic_json<> json
default JSON class
Definition: json.hpp:2355
static basic_json array(initializer_list_t init={})
explicitly create an array from an initializer list
Definition: json.hpp:15905

Output (play with this example online):
1
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/begin.cpp -o begin 
See also
cbegin() – returns a const iterator to the beginning
end() – returns an iterator to the end
cend() – returns a const iterator to the end
Since
version 1.0.0

Definition at line 18500 of file json.hpp.