json/api/basic_json/boolean_t.md

nlohmann::basic_json::boolean_t

using boolean_t = BooleanType;

The type used to store JSON booleans.

RFC 8259 implicitly describes a boolean as a type which differentiates the two literals #!json true and #!json false.

To store boolean values in C++, a type is defined by the template parameter BooleanType which chooses the type to use.

Template parameters

BooleanType

the type to store booleans. As it is stored directly inside a basic_json value (in a union), it must be a trivially default-constructible, trivially copyable, and trivially destructible type that is convertible to and from #!cpp bool. See Template Parameter Requirements.

Notes

Default type

With the default values for BooleanType (#!cpp bool), the default value for boolean_t is #!cpp bool.

Storage

Boolean values are stored directly inside a basic_json type.

Examples

??? example

The following code shows that `boolean_t` is by default, a typedef to `#!cpp bool`.
 
```cpp
#include <iostream>
#include <iomanip>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
{
    std::cout << std::boolalpha << std::is_same<bool, json::boolean_t>::value << std::endl;
}

```

Output:

```json
true

```

See also

• is_boolean checks whether the JSON value is a boolean

Version history

• Added in version 1.0.0.