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# nlohmann::byte_container_with_subtype::has_subtype

    constexpr bool has_subtype() const noexcept;

Returns whether the value has a subtype.

## Return value

whether the value has a subtype

## Exception safety

No-throw guarantee: this function never throws exceptions.

## Complexity

Constant.

## Examples

Example

The example below demonstrates how `has_subtype` can check whether a subtype was set.

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

    // define a byte container based on std::vector
    using byte_container_with_subtype = nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>;

    int main()
    {
        std::vector<std::uint8_t> bytes = {{0xca, 0xfe, 0xba, 0xbe}};

        // create container
        auto c1 = byte_container_with_subtype(bytes);

        // create container with subtype
        auto c2 = byte_container_with_subtype(bytes, 42);

        std::cout << std::boolalpha << "c1.has_subtype() = " << c1.has_subtype()
                  << "\nc2.has_subtype() = " << c2.has_subtype() << std::endl;
    }

Output:

    c1.has_subtype() = false
    c2.has_subtype() = true

## Version history

Since version 3.8.0.

Last update: May 17, 2022
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