:relfileprefix: ../../
[#boost-urls-param_pct_view]

== xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::param_pct_view


A query parameter


=== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/param.hpp#L638[boost/url/param.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
struct param_pct_view;
----

===  Member Functions
[cols=2,separator=¦]
|===
¦Name ¦Description
¦xref:boost/urls/param_pct_view/2conversion-00.adoc[`operator param`]  ¦

Conversion

¦xref:boost/urls/param_pct_view/2conversion-0c.adoc[`operator param_view`]  ¦

Conversion to param_view

¦xref:boost/urls/param_pct_view/operator_ptr.adoc[`operator->`]  ¦

Arrow support

¦xref:boost/urls/param_pct_view/2constructor.adoc[`param_pct_view`] [.small]#[constructor]# ¦

Construction


Constructor


aggregate construction

|===
===  Data Members
[cols=2,separator=¦]
|===
¦Name ¦Description
¦xref:boost/urls/param_pct_view/has_value.adoc[`has_value`]  ¦

True if a value is present

¦xref:boost/urls/param_pct_view/key.adoc[`key`]  ¦

The key

¦xref:boost/urls/param_pct_view/value.adoc[`value`]  ¦

The value

|===

=== Description


Objects of this type represent a single key
and value pair in a query string where a key
is always present and may be empty, while the
presence of a value is indicated by
xref:boost/urls/param_pct_view/has_value.adoc[has_value]
equal to true.
An empty value is distinct from no value.

The strings may have percent escapes, and
offer an additional invariant: they never
contain an invalid percent-encoding.

For most usages, key comparisons are
case-sensitive and duplicate keys in
a query are possible. However, it is
the authority that has final control
over how the query is interpreted.




Keys and values in this object reference
external character buffers.
Ownership of the buffers is not transferred;
the caller is responsible for ensuring that
the assigned buffers remain valid until
they are no longer referenced.
[,cpp]
----
query-params    = query-param *( "&" query-param )
query-param     = key [ "=" value ]
key             = *qpchar
value           = *( qpchar / "=" )
----

* link:https://en.wikipedia.org/wiki/Query_string[Query string (Wikipedia)]



=== See Also


xref:boost/urls/param.adoc[param]
,
xref:boost/urls/param_view.adoc[param_view]
.



