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

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


A view representing query parameters in a URL


== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_encoded_ref.hpp#L73[boost/url/params_encoded_ref.hpp,window=blank_]>`

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

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

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

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

The reference type

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

A signed integer type used to represent differences.

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

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

The reference type

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

An unsigned integer type to represent sizes.

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

The value type

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

Append params

¦xref:boost/urls/params_encoded_ref/assign.adoc[`assign`]  ¦

Assign params

¦xref:boost/urls/params_encoded_base/begin.adoc[`begin`]  ¦

Return an iterator to the beginning

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

Return the query corresponding to these params

¦xref:boost/urls/params_encoded_ref/clear.adoc[`clear`]  ¦

Clear the contents of the container

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

Return true if a matching key exists

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

Return the number of matching keys

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

Return true if there are no params

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

Return an iterator to the end

¦xref:boost/urls/params_encoded_ref/erase.adoc[`erase`]  ¦

Erase params

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

Find a matching key

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

Find a matching key

¦xref:boost/urls/params_encoded_ref/insert.adoc[`insert`]  ¦

Insert params

¦xref:boost/urls/params_encoded_ref/2conversion.adoc[`operator params_encoded_view`]  ¦

Conversion

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

Assignment

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

Constructor

¦xref:boost/urls/params_encoded_ref/replace.adoc[`replace`]  ¦

Replace params

¦xref:boost/urls/params_encoded_ref/set.adoc[`set`]  ¦

Set a value

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

Return the number of params

¦xref:boost/urls/params_encoded_ref/unset.adoc[`unset`]  ¦

Remove the value on an element

¦xref:boost/urls/params_encoded_ref/url.adoc[`url`]  ¦

Return the referenced url

|===
==  Static Member Functions
[cols=2,separator=¦]
|===
¦Name ¦Description
¦xref:boost/urls/params_encoded_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 value pairs.

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

The view is modifiable; calling non-const
members causes changes to the referenced
url.

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

params_encoded_ref p = u.encoded_params();
----

Strings produced when elements are returned
have type
xref:boost/urls/param_pct_view.adoc[param_pct_view]
and represent
encoded strings. Strings passed to member
functions may contain percent escapes, and
throw exceptions on invalid inputs.

=== Iterator Invalidation

Changes to the underlying character buffer
can invalidate iterators which reference it.
Modifications made through the container
invalidate some iterators to the underlying
character buffer:

* xref:boost/urls/params_encoded_ref/append-07.adoc[append]
: Only `end()`.

* xref:boost/urls/params_encoded_ref/assign-00.adoc[assign]
,
xref:boost/urls/params_encoded_ref/clear.adoc[clear]
,        `operator&equals;` : All params.

* xref:boost/urls/params_encoded_ref/erase-08.adoc[erase]
: Erased params and all
params after (including `end()`).

* xref:boost/urls/params_encoded_ref/insert-03.adoc[insert]
: All params at or after
the insertion point (including `end()`).

* xref:boost/urls/params_encoded_ref/replace-0f.adoc[replace]
,
xref:boost/urls/params_encoded_ref/set-07.adoc[set]
: Modified
params and all params
after (including `end()`).



