JSON for Modern C++ 3.10.4

◆ clear()

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>>
void nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::clear ( )
inlinenoexcept

Clears the content of a JSON value and resets it to the default value as if basic_json(value_t) would have been called with the current value type from type():

Value type initial value
null null
boolean false
string ""
number 0
binary An empty byte vector
object {}
array []
Postcondition
Has the same effect as calling
*this = basic_json(type());
basic_json(const value_t v)
create an empty value with a given type
Definition: json.hpp:18975
constexpr value_t type() const noexcept
return the type of the JSON value (explicit)
Definition: json.hpp:19972
Example
The example below shows the effect of clear() to different JSON types.
1#include <iostream>
2#include <nlohmann/json.hpp>
3
4using json = nlohmann::json;
5
6int main()
7{
8 // create JSON values
9 json j_null;
10 json j_boolean = true;
11 json j_number_integer = 17;
12 json j_number_float = 23.42;
13 json j_object = {{"one", 1}, {"two", 2}};
14 json j_array = {1, 2, 4, 8, 16};
15 json j_string = "Hello, world";
16
17 // call clear()
18 j_null.clear();
19 j_boolean.clear();
20 j_number_integer.clear();
21 j_number_float.clear();
22 j_object.clear();
23 j_array.clear();
24 j_string.clear();
25
26 // serialize the cleared values()
27 std::cout << j_null << '\n';
28 std::cout << j_boolean << '\n';
29 std::cout << j_number_integer << '\n';
30 std::cout << j_number_float << '\n';
31 std::cout << j_object << '\n';
32 std::cout << j_array << '\n';
33 std::cout << j_string << '\n';
34}
basic_json<> json
default JSON class
Definition: json.hpp:3472

Output (play with this example online):
null
false
0
0.0
{}
[]
""
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/clear.cpp -o clear 
Complexity
Linear in the size of the JSON value.
Iterator validity
All iterators, pointers and references related to this container are invalidated.
Exception safety
No-throw guarantee: this function never throws exceptions.
See also
see basic_json(value_t) – constructor that creates an object with the same value than calling clear()
Since
version 1.0.0

Definition at line 22883 of file json.hpp.