[#boost-urls-url_view_base-scheme]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/url_view_base.adoc[url_view_base]::scheme
:relfileprefix: ../../../
:mrdocs:

Return the scheme

== Synopsis

Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/url_view_base.hpp#L404[boost/url/url_view_base.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
core::string_view
scheme() const noexcept;
----

== Description

This function returns the scheme if it exists, without a trailing colon (':'). Otherwise it returns an empty string. Note that schemes are case‐insensitive, and the canonical form is lowercased.

== Example
[,cpp]
----
assert( url_view( "http://www.example.com" ).scheme() == "http" );
----
== Exception Safety
Throws nothing.

== BNF
[,cpp]
----
scheme          = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )

URI             = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

absolute-URI    = scheme ":" hier-part [ "?" query ]
----
== Specification
* https://datatracker.ietf.org/doc/html/rfc3986#section-3.1[]

== Return Value

The scheme as a string.

== See Also

xref:boost/urls/url_view_base/has_scheme.adoc[`has_scheme`], xref:boost/urls/url_view_base/scheme_id.adoc[`scheme_id`].


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