json/doc/mkdocs/docs/api/basic_json/is_primitive.md

nlohmann::basic_json::is_primitive

constexpr bool is_primitive() const noexcept;

This function returns #!cpp true if and only if the JSON type is primitive (string, number, boolean, #!json null, binary).

Return value

#!cpp true if type is primitive (string, number, boolean, #!json null, or binary), #!cpp false otherwise.

Exception safety

No-throw guarantee: this member function never throws exceptions.

Complexity

Constant.

Possible implementation

constexpr bool is_primitive() const noexcept
{
    return is_null() || is_string() || is_boolean() || is_number() || is_binary();
}

Notes

The term primitive stems from RFC 8259:

JSON can represent four primitive types (strings, numbers, booleans, and null) and two structured types (objects and arrays).

This library extends primitive types to binary types, because binary types are roughly comparable to strings. Hence, is_primitive() returns #!cpp true for binary values.

Examples

??? example

The following code exemplifies `is_primitive()` for all JSON types.

```cpp
--8<-- "examples/is_primitive.cpp"
```

Output:

```json
--8<-- "examples/is_primitive.output"
```

See also

• is_structured() returns whether JSON value is structured
• is_null() returns whether JSON value is null
• is_string() returns whether JSON value is a string
• is_boolean() returns whether JSON value is a boolean
• is_number() returns whether JSON value is a number
• is_binary() returns whether JSON value is a binary array

Version history

• Added in version 1.0.0.
• Extended to return #!cpp true for binary types in version 3.8.0.