json/api/basic_json/clear/index.md

nlohmann::basic_json::clear

void clear() noexcept;

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	[]

Has the same effect as calling

*this = basic_json(type());

Exception safety

No-throw guarantee: this function never throws exceptions.

Complexity

Linear in the size of the JSON value.

Notes

All iterators, pointers, and references related to this container are invalidated.

Examples

Example

The example below shows the effect of clear() to different JSON types.

#include <iostream>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
{
    // create JSON values
    json j_null;
    json j_boolean = true;
    json j_number_integer = 17;
    json j_number_float = 23.42;
    json j_object = {{"one", 1}, {"two", 2}};
    json j_array = {1, 2, 4, 8, 16};
    json j_string = "Hello, world";

    // call clear()
    j_null.clear();
    j_boolean.clear();
    j_number_integer.clear();
    j_number_float.clear();
    j_object.clear();
    j_array.clear();
    j_string.clear();

    // serialize the cleared values()
    std::cout << j_null << '\n';
    std::cout << j_boolean << '\n';
    std::cout << j_number_integer << '\n';
    std::cout << j_number_float << '\n';
    std::cout << j_object << '\n';
    std::cout << j_array << '\n';
    std::cout << j_string << '\n';
}

Output:

null
false
0
0.0
{}
[]
""

Version history

• Added in version 1.0.0.
• Added support for binary types in version 3.8.0.