--- product: Chilkat product_version: 11.7.0 language: pascal language_label: Lazarus Pascal class: Cache license: bundle deprecated: false reference_html: https://www.chilkatsoft.com/refdoc/pascal_CacheRef.html --- # Chilkat Cache — Lazarus Pascal — v11.7.0 > Chilkat 11.7.0 · language=pascal · class=Cache > Other versions: replace `11.7.0` in this URL. Other languages: `https://www.chilkatsoft.com/ai-docs/v/11.7.0//classes/Cache.md`. > Language-wide rules (install, unlock, error model, strings/bytes): `https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/guide.md`. ## Purpose **Store, retrieve, expire, and clean up cached text or binary data on disk.** `Chilkat.Cache` is a disk-based cache class for storing and retrieving text or binary items by unique key. It provides configurable cache roots, optional multi-level directory layout, expiration metadata, ETag metadata, cache lookup, fetch-status properties, expiration updates, and cleanup methods for deleting individual items, expired items, older items, or the entire cache. **Key-based storage** Store and retrieve cached items by unique key, without the application needing to manage the underlying cache filenames directly. **Text and binary data** Cache strings, byte data, files, or Chilkat buffer objects depending on the data form used by the application. **Expiration control** Associate cached items with expiration times, update expiration metadata, and check whether cached content is still usable. **ETag metadata** Store and retrieve ETag values for workflows that need HTTP-style cache validation or conditional re-fetch logic. **Configurable layout** Choose the cache root directory and use an optional multi-level directory structure to avoid too many files in a single folder. **Cleanup operations** Delete a single cached item, remove expired items, remove older items, or clear the entire cache when needed. **Common pattern:** Configure the cache root, choose the key used to identify each item, check whether a valid cached copy exists, fetch or regenerate the content when needed, store it with expiration and optional ETag metadata, and periodically clean up expired or old cached items. For an extended overview, see [Cache Class Overview](https://www.chilkatsoft.com/cache_class_overview.asp). ## Object creation, unlocking and error handling **Create / Free** ```pascal uses Chilkat.Cache; var obj: TCache; begin obj := TCache.Create; try if not obj.IsValid then raise Exception.Create('Failed to create a TCache instance.'); // ... use obj ... finally obj.Free; end; end; ``` `constructor Create;` Allocates the underlying CkCache object and returns a new TCache instance. Simply adding **Chilkat.Cache** to the unit's `uses` clause is enough to locate and bind to the Chilkat shared library (DLL / .so / .dylib) at runtime — no separate load step is required. Check `obj.IsValid` after calling `Create`; it is `False` if the underlying library could not be found/loaded or the object could not be allocated (for example, when unlicensed). `destructor Destroy; override;` Every TCache created by calling `Create` should eventually be released by calling `.Free` (inherited from `TObject`). The destructor automatically disposes the underlying CkCache handle. A native (unmanaged) memory leak occurs if the object is never freed. Call `Global.UnlockBundle` once at the start of the program, before using this or any other Chilkat class. Any string unlocks a fully functional 30-day trial; a purchased unlock code is used in production. See `guide.md` for the exact code in Lazarus Pascal. ## Members common to every Chilkat class Documented once per language in `common-members.md`; listed here so this page is self-contained. | Property | Signature | Access | Meaning | |---|---|---|---| | `DebugLogFilePath` | `property DebugLogFilePath: string read GetDebugLogFilePath write SetDebugLogFilePath;` | read/write | If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. | | `LastErrorHtml` | `property LastErrorHtml: string read GetLastErrorHtml;` | read-only | Provides HTML-formatted information about the last called method or property. | | `LastErrorText` | `property LastErrorText: string read GetLastErrorText;` | read-only | Provides plain text information about the last called method or property. | | `LastErrorXml` | `property LastErrorXml: string read GetLastErrorXml;` | read-only | Provides XML-formatted information about the last called method or property. | | `LastMethodSuccess` | `property LastMethodSuccess: Boolean read GetLastMethodSuccess write SetLastMethodSuccess;` | read/write | Indicates the success or failure of the most recent method call: `True` means success, `False` means failure. | | `VerboseLogging` | `property VerboseLogging: Boolean read GetVerboseLogging write SetVerboseLogging;` | read/write | If set to `True`, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. | | `Version` | `property Version: string read GetVersion;` | read-only | Version of the component/library, such as "10.1.0" | ## Member index | Member | Kind | Signature | |---|---|---| | `LastEtagFetched` | property, read-only | `property LastEtagFetched: string read GetLastEtagFetched;` | | `LastExpirationFetchedStr` | property, read-only | `property LastExpirationFetchedStr: string read GetLastExpirationFetchedStr;` | | `LastHitExpired` | property, read-only | `property LastHitExpired: Boolean read GetLastHitExpired;` | | `LastKeyFetched` | property, read-only | `property LastKeyFetched: string read GetLastKeyFetched;` | | `Level` | property, read/write | `property Level: Integer read GetLevel write SetLevel;` | | `NumRoots` | property, read-only | `property NumRoots: Integer read GetNumRoots;` | | `AddRoot` | method | `procedure AddRoot(const path: string);` | | `DeleteAll` | method | `function DeleteAll: Integer;` | | `DeleteAllExpired` | method | `function DeleteAllExpired: Integer;` | | `DeleteFromCache` | method | `function DeleteFromCache(const key: string): Boolean;` | | `DeleteOlderDt` | method | `// dt is a TCkDateTime object. function DeleteOlderDt(dt: TChilkatBase): Integer;` | | `DeleteOlderStr` | method | `function DeleteOlderStr(const dateTimeStr: string): Integer;` | | `FetchBd` | method | `// bd is a TBinData object. function FetchBd(const key: string;     bd: TChilkatBase): Boolean;` | | `FetchSb` | method | `// sb is a TStringBuilder object. function FetchSb(const key: string;     sb: TChilkatBase): Boolean;` | | `FetchText` | method | `function FetchText(const key: string): string;` | | `GetEtag` | method | `function GetEtag(const key: string): string;` | | `GetExpirationStr` | method | `function GetExpirationStr(const url: string): string;` | | `GetFilename` | method | `function GetFilename(const key: string): string;` | | `GetRoot` | method | `function GetRoot(index: Integer): string;` | | `IsCached` | method | `function IsCached(const key: string): Boolean;` | | `SaveBd` | method | `// bd is a TBinData object. function SaveBd(const key: string;     const expiration: string;     const etag: string;     bd: TChilkatBase): Boolean;` | | `SaveTextDt` | method | `// expireDateTime is a TCkDateTime object. function SaveTextDt(const key: string;     expireDateTime: TChilkatBase;     const eTag: string;     const itemTextData: string): Boolean;` | | `SaveTextNoExpire` | method | `function SaveTextNoExpire(const key: string;     const eTag: string;     const itemTextData: string): Boolean;` | | `SaveTextStr` | method | `function SaveTextStr(const key: string;     const expireDateTime: string;     const eTag: string;     const itemTextData: string): Boolean;` | | `UpdateExpirationDt` | method | `// expireDateTime is a TCkDateTime object. function UpdateExpirationDt(const key: string;     expireDateTime: TChilkatBase): Boolean;` | | `UpdateExpirationStr` | method | `function UpdateExpirationStr(const key: string;     const expireDateTime: string): Boolean;` | ## Properties ### Cache.LastEtagFetched `Chilkat 11.7.0 · pascal · Cache · LastEtagFetched · property · read-only` ```pascal property LastEtagFetched: string read GetLastEtagFetched; ``` Returns the ETag metadata associated with the most recently fetched cache item. An empty string means that the fetched item has no stored ETag. **Read after a fetch:** This property describes the item returned by the most recent successful fetch operation, such as `FetchBd`, `FetchSb`, or `FetchText`. **ETags are opaque metadata:** The cache stores and returns the string but does not interpret it. Applications commonly use an HTTP ETag with conditional requests such as `If-None-Match`. ### Cache.LastExpirationFetchedStr `Chilkat 11.7.0 · pascal · Cache · LastExpirationFetchedStr · property · read-only` ```pascal property LastExpirationFetchedStr: string read GetLastExpirationFetchedStr; ``` Returns the expiration date and time stored for the most recently fetched cache item, formatted as an RFC 822-style Internet date. An empty string represents an item with no expiration date. **Expiration is metadata:** Fetching an expired item is still possible. Read `LastHitExpired` after the fetch to determine whether the returned entry is stale. ### Cache.LastHitExpired `Chilkat 11.7.0 · pascal · Cache · LastHitExpired · property · read-only` ```pascal property LastHitExpired: Boolean read GetLastHitExpired; ``` Returns `True` when the expiration time of the most recently fetched item is earlier than the current system date and time; otherwise returns `False`. **Expired does not mean deleted:** Expiration marks an entry as stale. The file remains in the cache until it is replaced or removed by methods such as `DeleteAllExpired` or `DeleteFromCache`. ### Cache.LastKeyFetched `Chilkat 11.7.0 · pascal · Cache · LastKeyFetched · property · read-only` ```pascal property LastKeyFetched: string read GetLastKeyFetched; ``` Returns the application-defined key associated with the most recently fetched cache item. **Keys are not limited to URLs:** A canonicalized URL is a common key for cached web content, but any unique string may be used. Reusing a key causes a save operation to replace the existing item for that key. ### Cache.Level `Chilkat 11.7.0 · pascal · Cache · Level · property · read/write` ```pascal property Level: Integer read GetLevel write SetLevel; ``` Gets or sets the number of directory levels used beneath each cache root. Valid values are `0`, `1`, and `2`. | Value | Directory layout | | :--- | :--- | | `0` | All cache files are stored directly in the cache root. | | `1` | Files are distributed among 256 first-level directories named `0` through `255`. | | `2` | Files are distributed through two levels of 256 directories, allowing as many as 65,536 leaf directories per root. | **Configure before use:** Use the same level when reopening an existing cache. Changing the layout does not reorganize previously stored files and can prevent the object from locating them through their keys. ### Cache.NumRoots `Chilkat 11.7.0 · pascal · Cache · NumRoots · property · read-only` ```pascal property NumRoots: Integer read GetNumRoots; ``` Returns the number of cache-root directories that have been registered by calling `AddRoot`. **Multiple roots:** A cache may span more than one directory or storage device. Configure the same root set when reopening a persistent cache so previously stored items remain discoverable. ## Methods ### Cache.AddRoot `Chilkat 11.7.0 · pascal · Cache · AddRoot · method` ```pascal procedure AddRoot(const path: string); ``` Adds `path` as a root directory for the disk cache. Call this method once for each root that should participate in the cache. For example, a cache distributed across `D:\cacheRoot`, `E:\cacheRoot`, and `F:\cacheRoot` is configured by calling this method three times. **Use dedicated writable directories:** Cache cleanup methods can delete cache files beneath every configured root. Do not mix unrelated application files into a cache root. **Persistent configuration:** Recreate the same roots and `Level` setting before accessing a cache created by an earlier process or application run. ### Cache.DeleteAll `Chilkat 11.7.0 · pascal · Cache · DeleteAll · method` ```pascal function DeleteAll: Integer; ``` Deletes every cache item from all configured roots and returns the number of cache files removed. Multi-level subdirectories are retained. **Destructive operation:** This cannot be limited to a key prefix or reversed. Use cache roots dedicated to Chilkat cache data. ### Cache.DeleteAllExpired `Chilkat 11.7.0 · pascal · Cache · DeleteAllExpired · method` ```pascal function DeleteAllExpired: Integer; ``` Deletes all cache items whose stored expiration time is earlier than the current system time and returns the number of files removed. **Non-expiring entries remain:** Items saved without an expiration date are not removed by this method. ### Cache.DeleteFromCache `Chilkat 11.7.0 · pascal · Cache · DeleteFromCache · method` ```pascal function DeleteFromCache(const key: string): Boolean; ``` Deletes the cache item identified by `key`. | Return value | Meaning | | :--- | :--- | | `True` | The item was deleted, or no item existed for the key. | | `False` | The item exists but could not be deleted, for example because of a filesystem permission or sharing error. | **Idempotent deletion:** A missing key is not treated as an error, which makes it safe to call this method when the application merely wants to ensure that an item is absent. Returns True for success, False for failure. ### Cache.DeleteOlderDt `Chilkat 11.7.0 · pascal · Cache · DeleteOlderDt · method` ```pascal // dt is a TCkDateTime object. function DeleteOlderDt(dt: TChilkatBase): Integer; ``` Deletes cache items older than the cutoff date and time supplied in `dt`. Returns the number of cache files deleted, or `-1` if an error occurs. **Different from expiration cleanup:** Use `DeleteAllExpired` when the decision should be based specifically on each item's expiration metadata. ### Cache.DeleteOlderStr `Chilkat 11.7.0 · pascal · Cache · DeleteOlderStr · method` ```pascal function DeleteOlderStr(const dateTimeStr: string): Integer; ``` Deletes cache items older than the cutoff date and time supplied in `dateTimeStr` as an RFC 822-style Internet date string. Returns the number of cache files deleted, or `-1` if an error occurs. **Date format:** A typical value is `Mon, 03 Aug 2026 12:00:00 GMT`. Use `DeleteOlderDt` when the cutoff is already available as a `CkDateTime`. ### Cache.FetchBd `Chilkat 11.7.0 · pascal · Cache · FetchBd · method · since 9.5.0.91` ```pascal // bd is a TBinData object. function FetchBd(const key: string;     bd: TChilkatBase): Boolean; ``` Retrieves the binary item identified by `key` and loads its bytes into the `BinData` object supplied in `bd`. The key is application-defined, may contain any characters, and must uniquely identify the intended item. **Check the return value:** Use the destination only when this method returns `True`. A failed lookup or filesystem error returns `False`. **Freshness:** A successful fetch may return an expired item. Read `LastHitExpired` immediately afterward when stale data must not be used. Returns True for success, False for failure. ### Cache.FetchSb `Chilkat 11.7.0 · pascal · Cache · FetchSb · method · since 9.5.0.91` ```pascal // sb is a TStringBuilder object. function FetchSb(const key: string;     sb: TChilkatBase): Boolean; ``` Retrieves the text item identified by `key` and loads its content into the `StringBuilder` supplied in `sb`. The key is application-defined, may contain any characters, and must uniquely identify the intended item. **Check the return value:** Use the destination only when this method returns `True`. A failed lookup or filesystem error returns `False`. **Freshness:** A successful fetch may return an expired item. Read `LastHitExpired` immediately afterward when stale data must not be used. Returns True for success, False for failure. ### Cache.FetchText `Chilkat 11.7.0 · pascal · Cache · FetchText · method` ```pascal function FetchText(const key: string): string; ``` Retrieves the text item identified by `key` and returns its string content. The key is application-defined, may contain any characters, and must uniquely identify the intended item. **Freshness is separate:** A successful fetch can return an expired entry. Read `LastHitExpired` immediately afterward when the application requires only fresh data. Returns True for success, False for failure. ### Cache.GetEtag `Chilkat 11.7.0 · pascal · Cache · GetEtag · method` ```pascal function GetEtag(const key: string): string; ``` Returns the ETag metadata stored with the cache item identified by `key`. **Opaque value:** Chilkat does not parse or validate the ETag. An application may store any auxiliary string here, although HTTP entity tags are the common use case. Returns True for success, False for failure. ### Cache.GetExpirationStr `Chilkat 11.7.0 · pascal · Cache · GetExpirationStr · method` ```pascal function GetExpirationStr(const url: string): string; ``` Returns the expiration date and time stored for the item identified by `url`, formatted as an RFC 822-style Internet date string. **Argument name:** Some language bindings name `url` `url` for historical reasons. It is the cache key and does not need to be a URL. **No-expiration entries:** An empty stored expiration represents an item that does not expire automatically. Returns True for success, False for failure. ### Cache.GetFilename `Chilkat 11.7.0 · pascal · Cache · GetFilename · method` ```pascal function GetFilename(const key: string): string; ``` Returns the absolute filesystem path of the cache file associated with `key`. **Implementation detail:** Treat the returned path as diagnostic information. Applications should normally read, update, and delete entries through the `Cache` API rather than modifying cache files directly. Returns True for success, False for failure. ### Cache.GetRoot `Chilkat 11.7.0 · pascal · Cache · GetRoot · method` ```pascal function GetRoot(index: Integer): string; ``` Returns the directory path of the cache root at zero-based `index`. Valid indexes range from `0` through `NumRoots - 1`. Returns True for success, False for failure. ### Cache.IsCached `Chilkat 11.7.0 · pascal · Cache · IsCached · method` ```pascal function IsCached(const key: string): Boolean; ``` Returns `True` if an item exists for `key`, or `False` if the key is not present. **Presence is not freshness:** This method does not imply that the entry is unexpired. Fetch the item and examine `LastHitExpired`, or read its expiration metadata, when freshness matters. ### Cache.SaveBd `Chilkat 11.7.0 · pascal · Cache · SaveBd · method · since 11.0.0` ```pascal // bd is a TBinData object. function SaveBd(const key: string;     const expiration: string;     const etag: string;     bd: TChilkatBase): Boolean; ``` Stores the contents of `bd` as binary cache data under `key`. If the key already exists, its data and metadata are replaced. | Argument | Purpose | | :--- | :--- | | `key` | The unique application-defined cache key. | | `expiration` | Expiration as an RFC 822-style Internet date string. Pass an empty string for no expiration. | | `etag` | Optional ETag or application metadata. Pass an empty string when unused. | | `bd` | The `BinData` containing the bytes to save. | **Expiration is not automatic deletion:** An expired item remains present until it is replaced or explicitly removed. This permits stale-while-revalidate workflows but requires the application to check freshness. Returns True for success, False for failure. ### Cache.SaveTextDt `Chilkat 11.7.0 · pascal · Cache · SaveTextDt · method` ```pascal // expireDateTime is a TCkDateTime object. function SaveTextDt(const key: string;     expireDateTime: TChilkatBase;     const eTag: string;     const itemTextData: string): Boolean; ``` Stores `itemTextData` as a text cache item under `key`, with the expiration date and time supplied in `expireDateTime`. If the key already exists, its data and metadata are replaced. `eTag` is optional ETag or application metadata and may be an empty string. The key may contain any characters and may be any length, but it must uniquely identify the item. **Expiration does not delete:** After the expiration time passes, the entry remains on disk and can still be fetched. Use `LastHitExpired` to detect staleness and a deletion method to remove it. Returns True for success, False for failure. ### Cache.SaveTextNoExpire `Chilkat 11.7.0 · pascal · Cache · SaveTextNoExpire · method` ```pascal function SaveTextNoExpire(const key: string;     const eTag: string;     const itemTextData: string): Boolean; ``` Stores `itemTextData` as a non-expiring text cache item under `key`. If the key already exists, its data and metadata are replaced. `eTag` is optional ETag or application metadata and may be an empty string. Returns True for success, False for failure. ### Cache.SaveTextStr `Chilkat 11.7.0 · pascal · Cache · SaveTextStr · method` ```pascal function SaveTextStr(const key: string;     const expireDateTime: string;     const eTag: string;     const itemTextData: string): Boolean; ``` Stores `itemTextData` as a text cache item under `key`, with `expireDateTime` providing the expiration time as an RFC 822-style Internet date string. If the key already exists, its data and metadata are replaced. `eTag` is optional ETag or application metadata and may be empty. **Date alternatives:** Use `SaveTextDt` when the expiration is available as a `CkDateTime`, or `SaveTextNoExpire` for an entry without expiration. Returns True for success, False for failure. ### Cache.UpdateExpirationDt `Chilkat 11.7.0 · pascal · Cache · UpdateExpirationDt · method` ```pascal // expireDateTime is a TCkDateTime object. function UpdateExpirationDt(const key: string;     expireDateTime: TChilkatBase): Boolean; ``` Replaces the expiration date and time of the cache item identified by `key` with the `CkDateTime` value supplied in `expireDateTime`. The cached data and ETag are unchanged. **Existing item required:** This method updates metadata; it does not create a new cache entry when the key is absent. Returns True for success, False for failure. ### Cache.UpdateExpirationStr `Chilkat 11.7.0 · pascal · Cache · UpdateExpirationStr · method` ```pascal function UpdateExpirationStr(const key: string;     const expireDateTime: string): Boolean; ``` Replaces the expiration date and time of the cache item identified by `key` with the RFC 822-style Internet date string supplied in `expireDateTime`. The cached data and ETag are unchanged. **Argument name:** Some language bindings name `key` `url`; it is the cache key and does not need to be a URL. Use `UpdateExpirationDt` for a `CkDateTime` value. Returns True for success, False for failure. ## Related classes [`BinData`](https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/classes/BinData.md), [`CkDateTime`](https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/classes/CkDateTime.md), [`StringBuilder`](https://www.chilkatsoft.com/ai-docs/v/11.7.0/pascal/classes/StringBuilder.md)