# Poco

# template < class TKey, class TValue >

# class UniqueExpireStrategy

Library: Foundation
Package: Cache
Header: Poco/UniqueExpireStrategy.h

## Description

An UniqueExpireStrategy implements time based expiration of cache entries. In contrast to ExpireStrategy which only allows to set a per cache expiration value, it allows to define expiration per CacheEntry. Each TValue object must thus offer the following method:

    const Poco::Timestamp& getExpiration() const;

which returns the absolute timepoint when the entry will be invalidated.

## Inheritance

Direct Base Classes: AbstractStrategy < TKey, TValue >

All Base Classes: AbstractStrategy < TKey, TValue >

## Member Summary

Member Functions: onAdd, onClear, onGet, onIsValid, onRemove, onReplace

## Types Aliases

### ConstIndexIterator

using ConstIndexIterator = typename TimeIndex::const_iterator;

### IndexIterator

using IndexIterator = typename TimeIndex::iterator;

### Iterator

using Iterator = typename Keys::iterator;

### Keys

using Keys = std::map < TKey, IndexIterator >;

### TimeIndex

using TimeIndex = std::multimap < Timestamp, TKey >;

## Constructors

### UniqueExpireStrategy

UniqueExpireStrategy() = default;

Create an unique expire strategy.

## Destructor

### ~UniqueExpireStrategy

~UniqueExpireStrategy() = default;

## Member Functions

### onAdd

void onAdd(
const void * param417,
const KeyValueArgs < TKey, TValue > & args
);

### onClear

void onClear(
const void * param420,
const EventArgs & args
);

### onGet

void onGet(
const void * param419,
const TKey & key
);

### onIsValid

void onIsValid(
const void * param421,
ValidArgs < TKey > & args
);

### onRemove

void onRemove(
const void * param418,
const TKey & key
);

### onReplace

void onReplace(
const void * param422,
std::set < TKey > & elemsToRemove
);

## Variables

### _keyIndex

TimeIndex _keyIndex;

Maps time to key value

### _keys

Keys _keys;

For faster replacement of keys, the iterator points to the _keyIndex map