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

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


A view representing query parameters in a URL


== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_view.hpp#L47[boost/url/params_view.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
class params_view
    : public xref:boost/urls/params_base.adoc[params_base];
----

==  Types
[cols=2,separator=¦]
|===
¦Name ¦Description
¦xref:boost/urls/params_base/const_iterator.adoc[`const_iterator`]  ¦

xref:boost/urls/params_base/iterator.adoc[iterator]

¦xref:boost/urls/params_base/const_reference.adoc[`const_reference`]  ¦

The reference type

¦xref:boost/urls/params_base/difference_type.adoc[`difference_type`]  ¦

A signed integer type used to represent differences.

¦xref:boost/urls/params_base/iterator.adoc[`iterator`]  ¦

¦xref:boost/urls/params_base/reference.adoc[`reference`]  ¦

The reference type

¦xref:boost/urls/params_base/size_type.adoc[`size_type`]  ¦

An unsigned integer type to represent sizes.

¦xref:boost/urls/params_base/value_type.adoc[`value_type`]  ¦

The value type

|===
==  Member Functions
[cols=2,separator=¦]
|===
¦Name ¦Description
¦xref:boost/urls/params_base/begin.adoc[`begin`]  ¦

Return an iterator to the beginning

¦xref:boost/urls/params_base/buffer.adoc[`buffer`]  ¦

Return the referenced character buffer.

¦xref:boost/urls/params_base/contains.adoc[`contains`]  ¦

Return true if a matching key exists

¦xref:boost/urls/params_base/count.adoc[`count`]  ¦

Return the number of matching keys

¦xref:boost/urls/params_base/empty.adoc[`empty`]  ¦

Return true if there are no params

¦xref:boost/urls/params_base/end.adoc[`end`]  ¦

Return an iterator to the end

¦xref:boost/urls/params_base/find.adoc[`find`]  ¦

Find a matching key

¦xref:boost/urls/params_base/find_last.adoc[`find_last`]  ¦

Find a matching key

¦xref:boost/urls/params_view/operator_assign.adoc[`operator=`]  ¦

Assignment

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

Constructor

¦xref:boost/urls/params_base/size.adoc[`size`]  ¦

Return the number of params

|===
==  Static Member Functions
[cols=2,separator=¦]
|===
¦Name ¦Description
¦xref:boost/urls/params_base/max_size.adoc[`max_size`]  ¦

Return the maximum number of characters possible

|===

== Description


Objects of this type are used to interpret
the query parameters as a bidirectional view
of key&sol;value pairs.

The view does not retain ownership of the
elements and instead references the original
character buffer. The caller is responsible
for ensuring that the lifetime of the buffer
extends until it is no longer referenced.

=== Example
[,cpp]
----
url_view u( "?first=John&last=Doe" );

params_view p = u.params();
----

Percent escapes in strings returned when
dereferencing iterators are automatically
decoded.

=== Iterator Invalidation

Changes to the underlying character buffer
can invalidate iterators which reference it.