nlohmann::basic_json::swap¶

// (1)
void swap(reference other) noexcept;

// (2)
void swap(reference left, reference right) noexcept;

// (3)
void swap(array_t& other);

// (4)
void swap(object_t& other);

// (5)
void swap(string_t& other);

// (6)
void swap(binary_t& other);

// (7)
void swap(typename binary_t::container_type& other);

1. Exchanges the contents of the JSON value with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
2. Exchanges the contents of the JSON value from left with those of right. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated. Implemented as a friend function callable via ADL.
3. Exchanges the contents of a JSON array with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
4. Exchanges the contents of a JSON object with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
5. Exchanges the contents of a JSON string with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
6. Exchanges the contents of a binary value with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
7. Exchanges the contents of a binary value with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated. Unlike version (6), no binary subtype is involved.

Parameters¶

other (in, out)

value to exchange the contents with

left (in, out)

value to exchange the contents with

right (in, out)

value to exchange the contents with

Exceptions¶

1. No-throw guarantee: this function never throws exceptions.
2. No-throw guarantee: this function never throws exceptions.
3. Throws type_error.310 if called on JSON values other than arrays; example: "cannot use swap() with boolean"
4. Throws type_error.310 if called on JSON values other than objects; example: "cannot use swap() with boolean"
5. Throws type_error.310 if called on JSON values other than strings; example: "cannot use swap() with boolean"
6. Throws type_error.310 if called on JSON values other than binaries; example: "cannot use swap() with boolean"
7. Throws type_error.310 if called on JSON values other than binaries; example: "cannot use swap() with boolean"

Complexity¶

Constant.

Examples¶

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

using json = nlohmann::json;

int main()
{
    // create two JSON values
    json j1 = {1, 2, 3, 4, 5};
    json j2 = {{"pi", 3.141592653589793}, {"e", 2.718281828459045}};

    // swap the values
    j1.swap(j2);

    // output the values
    std::cout << "j1 = " << j1 << '\n';
    std::cout << "j2 = " << j2 << '\n';
}

j1 = {"e":2.718281828459045,"pi":3.141592653589793}
j2 = [1,2,3,4,5]

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

using json = nlohmann::json;

int main()
{
    // create a JSON value
    json value = {{"array", {1, 2, 3, 4}}};

    // create an array_t
    json::array_t array = {"Snap", "Crackle", "Pop"};

    // swap the array stored in the JSON value
    value["array"].swap(array);

    // output the values
    std::cout << "value = " << value << '\n';
    std::cout << "array = " << array << '\n';
}

value = {"array":["Snap","Crackle","Pop"]}
array = [1,2,3,4]

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

using json = nlohmann::json;

int main()
{
    // create a JSON value
    json value = { {"translation", {{"one", "eins"}, {"two", "zwei"}}} };

    // create an object_t
    json::object_t object = {{"cow", "Kuh"}, {"dog", "Hund"}};

    // swap the object stored in the JSON value
    value["translation"].swap(object);

    // output the values
    std::cout << "value = " << value << '\n';
    std::cout << "object = " << object << '\n';
}

value = {"translation":{"cow":"Kuh","dog":"Hund"}}
object = {"one":"eins","two":"zwei"}

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

using json = nlohmann::json;

int main()
{
    // create a JSON value
    json value = { "the good", "the bad", "the ugly" };

    // create string_t
    json::string_t string = "the fast";

    // swap the object stored in the JSON value
    value[1].swap(string);

    // output the values
    std::cout << "value = " << value << '\n';
    std::cout << "string = " << string << '\n';
}

value = ["the good","the fast","the ugly"]
string = the bad

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

using json = nlohmann::json;

int main()
{
    // create a binary value
    json value = json::binary({1, 2, 3});

    // create a binary_t
    json::binary_t binary = {{4, 5, 6}};

    // swap the object stored in the JSON value
    value.swap(binary);

    // output the values
    std::cout << "value = " << value << '\n';
    std::cout << "binary = " << json(binary) << '\n';
}

value = {"bytes":[4,5,6],"subtype":null}
binary = {"bytes":[1,2,3],"subtype":null}

See also¶

• std::swap<basic_json>

Version history¶

1. Since version 1.0.0.
2. Since version 1.0.0.
3. Since version 1.0.0.
4. Since version 1.0.0.
5. Since version 1.0.0.
6. Since version 3.8.0.
7. Since version 3.8.0.