boost::urls::param_pct_view :: Boost Libraries Documentation

# boost::urls::param_pct_view

A view of a percent‐encoded query parameter

## Synopsis

Declared in `<boost/url/param.hpp>`

    struct param_pct_view;

## 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 `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.

## BNF

    query-params    = query-param *( "&" query-param )
    query-param     = key [ "=" value ]
    key             = *qpchar
    value           = *( qpchar / "=" )

## Specification

- Query string (Wikipedia)

## Member Functions

Name | Description
`param_pct_view` [constructor] | Constructors
`operator‐>` | Arrow support
`operator param` | Conversion
`operator param_view` | Conversion to param_view

## Data Members

Name | Description
`has_value` | True if a value is present
`key` | The key
`value` | The value

## See Also

`param`, `param_view`.

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