Class YAHOO.widget.DataSource
- Known Subclasses:
-
YAHOO.widget.DS_XHR
YAHOO.widget.DS_JSFunction
YAHOO.widget.DS_JSArray
The DataSource classes manages sending a request and returning response from a live
database. Supported data include local JavaScript arrays and objects and databases
accessible via XHR connections. Supported response formats include JavaScript arrays,
JSON, XML, and flat-file textual data.
Constructor
YAHOO.widget.DataSource
(
)
Properties
_aCache
- private Object[]
Local cache of data result objects indexed chronologically.
_nIndex
- private static Number
Internal class variable to index multiple DataSource instances.
_sName
- private String
Name of DataSource instance.
Error message for null data responses.
Error message for data responses with parsing errors.
Max size of the local cache. Set to 0 to turn off caching. Caching is
useful to reduce the number of server connections. Recommended only for data
sources that return comprehensive results for queries or when stale data is
not an issue.
Default Value: 15
Enables case-sensitivity in the matching algorithm used against JS Array
types of DataSources and DataSource caches. If queryMatchCase is true, only
case-sensitive matches will return.
Default Value: false
Use this to fine-tune the matching algorithm used against JS Array types of
DataSource and DataSource caches. If queryMatchContains is true, then the JS
Array or cache returns results that "contain" the query string. By default,
queryMatchContains is set to false, so that only results that "start with"
the query string are returned.
Default Value: false
Enables query subset matching. If caching is on and queryMatchSubset is
true, substrings of queries will return matching cached results. For
instance, if the first query is for "abc" susequent queries that start with
"abc", like "abcd", will be queried against the cache, and not the live data
source. Recommended only for DataSources that return comprehensive results
for queries with very few characters.
Default Value: false
Methods
private
void
_addCacheElem
(
oResult
)
Adds a result object to the local cache, evicting the oldest element if the
cache is full. Newer items will have higher indexes, the oldest item will have
index of 0.
- Parameters:
-
oResult <Object>
Data result object, including array of results.
- Returns:
void
private
Object[]
_doQueryCache
(
oCallbackFn
,
sQuery
,
oParent
)
Queries the local cache for results. If query has been cached, the callback
function is called with the results, and the cached is refreshed so that it
is now the newest element.
- Parameters:
-
oCallbackFn <HTMLFunction>
Callback function defined by oParent object to which to return results.
-
sQuery <String>
Query string.
-
oParent <Object>
The object instance that has requested data.
- Returns:
Object[]
- aResults Array of results from local cache if found, otherwise null.
private
void
_init
(
)
Initializes DataSource instance.
void
doQuery
(
oCallbackFn
,
sQuery
,
oParent
)
Abstract method implemented by subclasses to make a query to the live data
source. Must call the callback function with the response returned from the
query. Populates cache (if enabled).
- Parameters:
-
oCallbackFn <HTMLFunction>
Callback function implemented by oParent to which to return results.
-
sQuery <String>
Query string.
-
oParent <Object>
The object instance that has requested data.
- Returns:
void
void
flushCache
(
)
Flushes cache.
void
getResults
(
oCallbackFn
,
sQuery
,
oParent
)
Retrieves query results, first checking the local cache, then making the
query request to the live data source as defined by the function doQuery.
- Parameters:
-
oCallbackFn <HTMLFunction>
Callback function defined by oParent object to which to return results.
-
sQuery <String>
Query string.
-
oParent <Object>
The object instance that has requested data.
- Returns:
void
String
toString
(
)
Public accessor to the unique name of the DataSource instance.
- Returns:
String
- Unique name of the DataSource instance
Events
cacheFlushEvent
(
oSelf
)
Fired when the local cache is flushed.
- Parameters:
-
oSelf <Object>
The DataSource instance
cacheQueryEvent
(
oSelf
,
oParent
,
sQuery
)
Fired when a query is made to the local cache.
- Parameters:
-
oSelf <Object>
The DataSource instance.
-
oParent <Object>
The requesting object.
-
sQuery <String>
The query string.
dataErrorEvent
(
oSelf
,
oParent
,
sQuery
,
sMsg
)
Fired when an error is encountered with the live data source.
- Parameters:
-
oSelf <Object>
The DataSource instance.
-
oParent <Object>
The requesting object.
-
sQuery <String>
The query string.
-
sMsg <String>
Error message string
getCachedResultsEvent
(
oSelf
,
oParent
,
sQuery
,
aResults
)
Fired when data is retrieved from the local cache.
- Parameters:
-
oSelf <Object>
The DataSource instance.
-
oParent <Object>
The requesting object.
-
sQuery <String>
The query string.
-
aResults <Object[]>
Array of result objects.
getResultsEvent
(
oSelf
,
oParent
,
sQuery
,
aResults
)
Fired when data is retrieved from the live data source.
- Parameters:
-
oSelf <Object>
The DataSource instance.
-
oParent <Object>
The requesting object.
-
sQuery <String>
The query string.
-
aResults <Object[]>
Array of result objects.
queryEvent
(
oSelf
,
oParent
,
sQuery
)
Fired when a query is made to the live data source.
- Parameters:
-
oSelf <Object>
The DataSource instance.
-
oParent <Object>
The requesting object.
-
sQuery <String>
The query string.