bslstl_isconvertibletostringview

Detailed Description

Provide a compile-time check for types convertible to string_view.

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Determine If a Type Is Convertible to a String View

Purpose

Provide a compile-time check for types convertible to string_view.

Classes

• bslstl::IsConvertibleToStringView: meta-function for string_view conversion

See also

bslmf_isconvertible, bslstl_isconvertibletocstring, bslstl_stringview

Description

This component provides a meta-function, bslstl::IsConvertibleToStringView, that may be used to query (at compile-time) whether a type is convertible to a bsl::basic_string_view<CHAR_TYPE, CHAR_TRAITS>.

bslstl::IsConvertibleToStringView meets the requirements of the UnaryTypeTrait concept defined in the C++ standard [meta.rqmts] with a base characteristic of bsl::true_type if the (template parameter) TYPE is convertible to bsl::basic_string_view<CHAR_TYPE, CHAR_TRAITS>, and a base characteristic of bsl::false_type otherwise.

This trait is particularly useful for implementing functions that accept "string-view-like" types, as specified in C++17 and later standards.

Usage

In this section we show the intended use of this component.

Example 1: Determine If a Type Is Convertible to a String View

Suppose that we want to determine whether various types are convertible to bsl::string_view.

First, we note that bsl::string_view itself is convertible:

assert((bslstl::IsConvertibleToStringView<char,
                                          std::char_traits<char>,
                                          bsl::string_view>::value));

Next, we verify that const char * is convertible to string_view:

assert((bslstl::IsConvertibleToStringView<char,
                                          std::char_traits<char>,
                                          const char *>::value));

Finally, we verify that an unrelated type is not convertible:

assert((!bslstl::IsConvertibleToStringView<char,
                                           std::char_traits<char>,
                                           int>::value));