[#boost-urls-param_pct_view-2constructor-05]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/param_pct_view.adoc[param_pct_view]::param_pct_view
:relfileprefix: ../../../
:mrdocs:

Constructor

== Synopsis

Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/param.hpp#L810[boost/url/param.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class OptionalString>
param_pct_view(
    xref:boost/urls/pct_string_view.adoc[pct_string_view] key,
    OptionalString const& value);
----

== Description

This constructs a parameter with a key and optional value, which may both contain percent escapes.

The new key and value reference the same corresponding underlying 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.

== Example
[,cpp]
----
param_pct_view qp( "key", optional<core::string_view>("value") );
----
== Postconditions
[,cpp]
----
this->key.data() == key.data() && this->value->data() == value->data() && this->has_value == true
----
== Complexity
Linear in `key&period;size() &plus; value&hyphen;&gt;size()`&period;

== Exception Safety
Exceptions thrown on invalid input&period;

== Exceptions

[cols=2]
|===
| Name
| Thrown on
| `system&lowbar;error`
| `key` or `value` contains an invalid percent&hyphen;encoding&period;
|===

== Return Value

A param object

== Template Parameters

[cols=2]
|===
| Name
| Description
| *OptionalString*
| An optional `core&colon;&colon;string&lowbar;view` type, such as `boost&colon;&colon;optional&lt;core&colon;&colon;string&lowbar;view&gt;` or `std&colon;&colon;optional&lt;core&colon;&colon;string&lowbar;view&gt;`&period;
|===

== Parameters

[cols=2]
|===
| Name
| Description
| *key*
| The key to set&period;
| *value*
| The optional value to set&period;
|===


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