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

Return the scheme

== Synopsis

Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/url_view_base.hpp#L454[boost&sol;url&sol;url&lowbar;view&lowbar;base&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/scheme.adoc[urls::scheme]
scheme&lowbar;id() const noexcept;
----

== Description

This function returns a value which depends on the scheme in the url&colon;

* If the scheme is a well&hyphen;known scheme, corresponding value from the enumeration `urls&colon;&colon;scheme` is returned&period;
* If a scheme is present but is not a well&hyphen;known scheme, the value returned is `urls&colon;&colon;scheme&colon;&colon;unknown`&period;
* Otherwise, if the scheme is absent the value returned is `urls&colon;&colon;scheme&colon;&colon;none`&period;

== Example
[,cpp]
----
assert( url_view( "wss://www.example.com/crypto.cgi" ).scheme_id() == scheme::wss );
----
== Complexity
Constant&period;

== Exception Safety
Throws nothing&period;

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

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

scheme          = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
----
== Specification
* https://datatracker.ietf.org/doc/html/rfc3986#section-3.1[]

== Return Value

The scheme as an enumeration value&period;

== See Also

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


[.small]#Created with https://www.mrdocs.com[MrDocs]#
