api/basic_json/operator=/index.md

# nlohmann::basic_json::operator=

```
basic_json& operator=(basic_json other) noexcept (
    std::is_nothrow_move_constructible<value_t>::value &&
    std::is_nothrow_move_assignable<value_t>::value &&
    std::is_nothrow_move_constructible<json_value>::value &&
    std::is_nothrow_move_assignable<json_value>::value &&
    std::is_nothrow_move_assignable<json_base_class_t>::value
);
```

Copy assignment operator. Copies a JSON value via the "copy and swap" strategy: It is expressed in terms of the copy constructor, destructor, and the `swap()` member function.

## Parameters

`other` (in) : value to copy from

## Exception safety

Strong guarantee: if an exception is thrown while copying `other`, there are no changes to `*this`.

## Complexity

Linear.

## Examples

Example

The code below shows and example for the copy assignment. It creates a copy of value `a` which is then swapped with `b`. Finally, the copy of `a` (which is the null value after the swap) is destroyed.

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

using json = nlohmann::json;

int main()
{
    // create JSON values
    json a = 23;
    json b = 42;

    // copy-assign a to b
    b = a;

    // serialize the JSON arrays
    std::cout << a << '\n';
    std::cout << b << '\n';
}
```

Output:

```
23
23
```

## See also

- [basic_json](https://json.nlohmann.me/api/basic_json/basic_json/index.md) create a JSON value
- [swap](https://json.nlohmann.me/api/basic_json/swap/index.md) exchanges the contents of two JSON values

## Version history

- Added in version 1.0.0.