[#boost-urls-url_base-set_scheme]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/url_base.adoc[url_base]::set_scheme
:relfileprefix: ../../../
:mrdocs:


Set the scheme

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/url_base.hpp#L244[boost/url/url_base.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/url_base.adoc[url_base]&
set_scheme(core::string_view s);
----

== Description


The scheme is set to the specified        string, which must contain a valid        scheme without any trailing colon        (':').        Note that schemes are case‐insensitive,        and the canonical form is lowercased.


=== Example

[,cpp]
----
assert( url( "http://www.example.com" ).set_scheme( "https" ).scheme_id() == scheme::https );
----

=== Complexity

Linear in `this‐>size() + s.size()`.


=== Exception Safety

Strong guarantee.        Calls to allocate may throw.        Exceptions thrown on invalid input.


=== BNF

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

=== Specification

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



== Exceptions


|===
| Name | Thrown on

| `system_error`
| `s` contains an invalid scheme.


|===

== Parameters


|===
| Name | Description

| *s*
| The scheme to set.


|===

== See Also


xref:boost/urls/url_base/remove_scheme.adoc[remove_scheme].






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