Cache Ruby Reference Documentation

CkCache

Current Version: 11.5.0
Requires Chilkat Bundle License

Chilkat.Cache

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.

Object Creation

obj = Chilkat::CkCache.new()

Properties

DebugLogFilePath
# strVal is a string
# ckStr is a CkString
cache.get_DebugLogFilePath(ckStr);
strVal = cache.debugLogFilePath();
cache.put_DebugLogFilePath(strVal);

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

  • A timeout property set to 0, indicating an infinite timeout.
  • A hang occurring within an event callback in the application code.
  • An internal bug in the Chilkat code causing the hang.

More Information and Examples
Example showing how to use DebugLogFilePath.
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LastErrorHtml
# strVal is a string
# ckStr is a CkString
cache.get_LastErrorHtml(ckStr);
strVal = cache.lastErrorHtml();

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorText
# strVal is a string
# ckStr is a CkString
cache.get_LastErrorText(ckStr);
strVal = cache.lastErrorText();

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

More Information and Examples
Concept of LastErrorTextLastErrorText Standard Information
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LastErrorXml
# strVal is a string
# ckStr is a CkString
cache.get_LastErrorXml(ckStr);
strVal = cache.lastErrorXml();

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastEtagFetched
# strVal is a string
# ckStr is a CkString
cache.get_LastEtagFetched(ckStr);
strVal = cache.lastEtagFetched();

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.

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LastExpirationFetchedStr
# strVal is a string
# ckStr is a CkString
cache.get_LastExpirationFetchedStr(ckStr);
strVal = cache.lastExpirationFetchedStr();

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.

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LastHitExpired
# boolVal is a boolean
boolVal = cache.get_LastHitExpired();

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.

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LastKeyFetched
# strVal is a string
# ckStr is a CkString
cache.get_LastKeyFetched(ckStr);
strVal = cache.lastKeyFetched();

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.

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LastMethodSuccess
# boolVal is a boolean
boolVal = cache.get_LastMethodSuccess();
cache.put_LastMethodSuccess(boolVal);

Indicates the success or failure of the most recent method call: true means success, false means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.

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Level
# intVal is an integer
intVal = cache.get_Level();
cache.put_Level(intVal);

Gets or sets the number of directory levels used beneath each cache root. Valid values are 0, 1, and 2.

ValueDirectory layout
0All cache files are stored directly in the cache root.
1Files are distributed among 256 first-level directories named 0 through 255.
2Files 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.

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NumRoots
# intVal is an integer
intVal = cache.get_NumRoots();

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.

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Utf8
# boolVal is a boolean
boolVal = cache.get_Utf8();
cache.put_Utf8(boolVal);

When set to true, all string arguments and return values are interpreted as UTF-8 strings. When set to false, they are interpreted as ANSI strings.

In Chilkat v11.0.0 and later, the default value is true. Before v11.0.0, it was false.

More Information and Examples
Strings in Ruby: Encoding, UTF-8, and Source File Format Considerations
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VerboseLogging
# boolVal is a boolean
boolVal = cache.get_VerboseLogging();
cache.put_VerboseLogging(boolVal);

If set to true, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is false. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
# strVal is a string
# ckStr is a CkString
cache.get_Version(ckStr);
strVal = cache.version();

Version of the component/library, such as "10.1.0"

More Information and Examples
How to get the Chilkat version at runtime.
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Methods

AddRoot
# path is a string
cache.AddRoot(path);

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.
More Information and Examples
Large Persistent Hash Table Stored on Filesystem
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DeleteAll
retInt = cache.DeleteAll();

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.
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DeleteAllExpired
retInt = cache.DeleteAllExpired();

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.
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DeleteFromCache
# key is a string
status = cache.DeleteFromCache(key);

Deletes the cache item identified by key.

Return valueMeaning
trueThe item was deleted, or no item existed for the key.
falseThe 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.

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DeleteOlderDt
# dateTime is a CkDateTime
retInt = cache.DeleteOlderDt(dateTime);

Deletes cache items older than the cutoff date and time supplied in dateTime.

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.
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DeleteOlderStr
# dateTimeStr is a string
retInt = cache.DeleteOlderStr(dateTimeStr);

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.
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FetchBd
# key is a string
# bd is a CkBinData
status = cache.FetchBd(key, bd);
Introduced in version 9.5.0.91

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.

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FetchSb
# key is a string
# sb is a CkStringBuilder
status = cache.FetchSb(key, sb);
Introduced in version 9.5.0.91

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.

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FetchText
# key is a string
# outStr is a CkString (output)
status = cache.FetchText(key, outStr);
retStr = cache.fetchText(key);

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.

More Information and Examples
Large Persistent Hash Table Stored on Filesystem
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GetEtag
# key is a string
# outStr is a CkString (output)
status = cache.GetEtag(key, outStr);
retStr = cache.getEtag(key);

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.

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GetExpirationStr
# url is a string
# outStr is a CkString (output)
status = cache.GetExpirationStr(url, outStr);
retStr = cache.getExpirationStr(url);

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.

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GetFilename
# key is a string
# outStr is a CkString (output)
status = cache.GetFilename(key, outStr);
retStr = cache.getFilename(key);

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.

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GetRoot
# index is an integer
# outStr is a CkString (output)
status = cache.GetRoot(index, outStr);
retStr = cache.getRoot(index);

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.

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IsCached
# key is a string
retBool = cache.IsCached(key);

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.
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SaveBd
# key is a string
# expiration is a string
# etag is a string
# bd is a CkBinData
status = cache.SaveBd(key, expiration, etag, bd);
Introduced in version 11.0.0

Stores the contents of bd as binary cache data under key. If the key already exists, its data and metadata are replaced.

ArgumentPurpose
keyThe unique application-defined cache key.
expirationExpiration as an RFC 822-style Internet date string. Pass an empty string for no expiration.
etagOptional ETag or application metadata. Pass an empty string when unused.
bdThe 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.

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SaveTextDt
# key is a string
# expireDateTime is a CkDateTime
# eTag is a string
# itemTextData is a string
status = cache.SaveTextDt(key, expireDateTime, eTag, itemTextData);

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.

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SaveTextNoExpire
# key is a string
# eTag is a string
# itemTextData is a string
status = cache.SaveTextNoExpire(key, eTag, itemTextData);

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.

More Information and Examples
Large Persistent Hash Table Stored on Filesystem
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SaveTextStr
# key is a string
# expireDateTime is a string
# eTag is a string
# itemTextData is a string
status = cache.SaveTextStr(key, expireDateTime, eTag, itemTextData);

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.

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UpdateExpirationDt
# key is a string
# expireDateTime is a CkDateTime
status = cache.UpdateExpirationDt(key, expireDateTime);

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.

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UpdateExpirationStr
# key is a string
# expireDateTime is a string
status = cache.UpdateExpirationStr(key, expireDateTime);

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.

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Deprecated

FetchFromCache Deprecated
# key is a string
# outBytes is a CkByteData (output)
status = cache.FetchFromCache(key, outData);

Retrieves the binary item identified by key from the disk cache and returns its bytes. The key may contain any characters and may be any length, but it must uniquely identify the intended item.

Empty data versus failure: In language bindings where failure is represented by an empty or null byte array, check the binding's normal success indicator, such as LastMethodSuccess, when an empty cached item is valid.

Returns true for success, false for failure.

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GetExpirationDt
# returns a CkDateTime
# key is a string
ret_ckDateTime = cache.GetExpirationDt(key);
This method is deprecated.

Deprecated: Use GetExpirationStr and load the returned value into a CkDateTime when an object representation is required.

Returns the expiration date and time for the item identified by key as a newly returned CkDateTime object.

Returns nil on failure

More Information and Examples
Replace Deprecated GetExpirationDt
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SaveToCacheDt Deprecated
# key is a string
# expireDateTime is a CkDateTime
# eTag is a string
# itemData is a CkByteData
status = cache.SaveToCacheDt(key, expireDateTime, eTag, itemData);

Stores itemData as binary cache data under key, using expireDateTime as the expiration date and time. If the key already exists, its data and metadata are replaced.

eTag is optional ETag or application metadata and may be empty.

Returns true for success, false for failure.

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SaveToCacheNoExpire Deprecated
# key is a string
# eTag is a string
# itemData is a CkByteData
status = cache.SaveToCacheNoExpire(key, eTag, itemData);

Stores itemData as non-expiring binary cache data under key. If the key already exists, its data and metadata are replaced. eTag is optional ETag or application metadata and may be empty.

Returns true for success, false for failure.

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SaveToCacheStr Deprecated
# key is a string
# expireDateTime is a string
# eTag is a string
# itemData is a CkByteData
status = cache.SaveToCacheStr(key, expireDateTime, eTag, itemData);

Stores itemData as binary cache data 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. Some language bindings name key url; it is the cache key and need not be a URL.

Returns true for success, false for failure.

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