std::basic_format_args
| Defined in header <format>
|
||
| template< class Context > class basic_format_args; |
(1) | (since C++20) |
| using format_args = basic_format_args<std::format_context>; |
(2) | (since C++20) |
| using wformat_args = basic_format_args<std::wformat_context>; |
(3) | (since C++20) |
Provides access to formatting arguments.
Member functions
| (constructor) |
constructs a basic_format_args object (public member function) |
| get |
returns formatting argument at the given index (public member function) |
std::basic_format_args::basic_format_args
| template< class... Args > basic_format_args( const /*format-arg-store*/<Context, Args...>& store ) noexcept; |
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Constructs a basic_format_args object from the result of a call to std::make_format_args or std::make_wformat_args.
std::basic_format_args::get
| std::basic_format_arg<Context> get( std::size_t i ) const noexcept; |
||
Returns a std::basic_format_arg holding the i-th argument in args, where args is the parameter pack passed to std::make_format_args or std::make_wformat_args.
If there's no such formatting argument (i.e. *this was default-constructed or i is not less than the number of formatting arguments), returns a default-constructed std::basic_format_arg (holding a std::monostate object).
Deduction guides
| template< class Context, class... Args > basic_format_args( /*format-arg-store*/<Context, Args...> ) -> basic_format_args<Context>; |
(since C++20) | |
Notes
std::basic_format_args has reference semantics. It is the programmer's responsibility to ensure that *this does not outlive store (which, in turn, should not outlive the arguments to std::make_format_args or std::make_wformat_args).
Example
| This section is incomplete Reason: no example |
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| P2216R3 | C++20 | format_args_t was provided due to overparameterization of vformat_to
|
removed |
| LWG 3810 | C++20 | basic_format_args has no deduction guide
|
added |
| LWG 4106 | C++20 | basic_format_args was default-constructible
|
default constructor removed |
See also
| (C++20) |
class template that provides access to a formatting argument for user-defined formatters (class template) |