pqxx::no_null< TYPE > Struct Template Reference

Nullness traits describing a type which does not have a null value. More...

#include <strconv.hxx>

Inheritance diagram for pqxx::no_null< TYPE >:

Static Public Member Functions
static constexpr bool	is_null (TYPE const &) noexcept
	Does a given value correspond to an SQL null value? More...

Static Public Attributes
static constexpr bool	has_null = false
	Does TYPE have a "built-in null value"? More...
static constexpr bool	always_null = false
	Are all values of this type null? More...

Detailed Description

template<typename TYPE>
struct pqxx::no_null< TYPE >

Nullness traits describing a type which does not have a null value.

Member Function Documentation

is_null()

template<typename TYPE >

static constexpr bool pqxx::no_null< TYPE >::is_null ( TYPE const &  )

staticconstexprnoexcept

Does a given value correspond to an SQL null value?

Most C++ types, such as int or std::string, have no inherent null value. But some types such as C-style string pointers do have a natural equivalent to an SQL null.

Member Data Documentation

always_null

template<typename TYPE >

constexpr bool pqxx::no_null< TYPE >::always_null = false

staticconstexpr

Are all values of this type null?

There are a few special C++ types which are always null - mainly std::nullptr_t.

has_null

template<typename TYPE >

constexpr bool pqxx::no_null< TYPE >::has_null = false

staticconstexpr

Does TYPE have a "built-in null value"?

For example, a pointer can equal nullptr, which makes a very natural representation of an SQL null value. For such types, the code sometimes needs to make special allowances.

for most types, such as int or std::string, there is no built-in null. If you want to represent an SQL null value for such a type, you would have to wrap it in something that does have a null value. For example, you could use std::optional<int> for "either an @c int or a null value."

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The documentation for this struct was generated from the following file:

• strconv.hxx