JSON for Modern C++  3.7.0

◆ 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>
void nlohmann::basic_json::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
object {}
array []
Postcondition
Has the same effect as calling
*this = basic_json(type());
Example
The example below shows the effect of clear() to different JSON types.
1 #include <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int 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:2355

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
basic_json(value_t) – constructor that creates an object with the same value than calling clear()
Since
version 1.0.0

Definition at line 19161 of file json.hpp.