[#boost-urls-url_view_base-scheme]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/url_view_base.adoc[url&lowbar;view&lowbar;base]::scheme
:relfileprefix: ../../../
:mrdocs:


Return the scheme

== Synopsis


Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/url_view_base.hpp#L387[boost&sol;url&sol;url&lowbar;view&lowbar;base&period;hpp]&gt;`

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

== Description


This function returns the scheme if it        exists, without a trailing colon (&apos;&colon;&apos;)&period;        Otherwise it returns an empty string&period;        Note that schemes are case&hyphen;insensitive,        and the canonical form is lowercased&period;


=== Example

[,cpp]
----
assert( url_view( "http://www.example.com" ).scheme() == "http" );
----

=== Exception Safety

Throws nothing&period;


=== BNF

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

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

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

=== Specification

* link:https://datatracker.ietf.org/doc/html/rfc3986#section-3.1[3&period;1&period; Scheme (rfc3986)]

Return the scheme

This function returns the scheme if it        exists, without a trailing colon (&apos;&colon;&apos;)&period;        Otherwise it returns an empty string&period;        Note that schemes are case&hyphen;insensitive,        and the canonical form is lowercased&period;


=== Example

[,cpp]
----
assert( url_view( "http://www.example.com" ).scheme() == "http" );
----

=== Exception Safety

Throws nothing&period;


=== BNF

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

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

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

=== Specification

* link:https://datatracker.ietf.org/doc/html/rfc3986#section-3.1[3&period;1&period; Scheme (rfc3986)]



== See Also


xref:boost/urls/url_view_base/has_scheme.adoc[has&lowbar;scheme],            xref:boost/urls/url_view_base/scheme_id.adoc[scheme&lowbar;id]&period;



xref:boost/urls/url_view_base/has_scheme.adoc[has&lowbar;scheme],            xref:boost/urls/url_view_base/scheme_id.adoc[scheme&lowbar;id]&period;






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