The QSparqlResult class provides an abstract interface for accessing the results of an executed QSparqlQuery. More...
Public Types |
|
| enum | Feature { QuerySize, ForwardOnly, Sync } |
Signals |
|
| void | dataReady (int totalCount) |
| void | finished () |
Public Member Functions |
|
| virtual | ~QSparqlResult () |
| int | pos () const |
| virtual bool | setPos (int pos) |
| virtual bool | next () |
| virtual bool | previous () |
| virtual bool | first () |
| virtual bool | last () |
| virtual int | size () const |
| bool | isValid () const |
| virtual QSparqlResultRow | current () const =0 |
| virtual QSparqlBinding | binding (int i) const =0 |
| virtual QVariant | value (int i) const =0 |
| virtual QString | stringValue (int i) const |
| bool | boolValue () const |
| virtual void | waitForFinished () |
| virtual bool | isFinished () const |
| bool | hasError () const |
| QSparqlError | lastError () const |
| QString | query () const |
| QSparqlQuery::StatementType | statementType () const |
| Returns the statement type of this QSparqlResult object. |
|
| bool | isTable () const |
| bool | isGraph () const |
| bool | isBool () const |
| virtual bool | hasFeature (QSparqlResult::Feature feature) const |
Protected Member Functions |
|
| QSparqlResult () | |
| void | setQuery (const QString &query) |
| void | setStatementType (QSparqlQuery::StatementType type) |
| Sets the statement type of this QSparqlResult object. |
|
| void | setLastError (const QSparqlError &e) |
| void | setBoolValue (bool v) |
| void | updatePos (int pos) |
Friends |
|
| class | QSparqlResultPrivate |
| class | QSparqlConnection |
| class | QSparqlConnectionPrivate |
The QSparqlResult class provides an abstract interface for accessing the results of an executed QSparqlQuery.
When QSparqlConnection::exec() is called, it asynchronously begins the execution of the given query. The returned result is in an unfinished state so that isFinished() returns false. When the execution finished, QSparqlResult emits the finished() signal and sets itself to finished state.
Initially, QSparqlResult is positioned on an invalid position. It must be navigated to a valid position (so that isValid() returns true) before values can be retrieved.
Navigating the result is performed with the following functions:
Retrieving the data is performed with the following functions:
This enum contains a list of features a QSparqlResult might support. Use hasFeature() to query whether a feature is supported or not. The supported features depend on the driver and whether the result was obtained via QSparqlConnection::exec() or QSparqlConnection::syncExec().
| QuerySize |
Whether the QSparqlResult can report the number of results of the query. |
| ForwardOnly |
Whether the result can only be navigated forward (i.e., using QSparqlResult::next()). |
| Sync |
Whether the result is natively synchronous (was retrieved via QSparqlConnection::syncExec() of natively synchronous connection). In this case, QSparqlResult::next() will fetch the next result synchronously.
|
| QSparqlResult::~QSparqlResult | ( | ) | [virtual] |
Destroys the object and frees any allocated resources.
| QSparqlResult::QSparqlResult | ( | ) | [protected] |
Creates a QSparqlResult. The result is empty, positioned at "before first row" and unfinished.
| QSparqlBinding QSparqlResult::binding | ( | int | index | ) | const [pure virtual] |
Returns the binding index in the current result row.
The bindings are numbered from left to right using the text of the SELECT statement. The indexes start from 0.
An invalid QSparqlBinding is returned if binding index does not exist, if the query is inactive, or if the query is positioned on an invalid result row.
| bool QSparqlResult::boolValue | ( | ) | const |
Returns the boolean result of an ASK query.
Note that this should only be used when isFinished() is true.
| QSparqlResultRow QSparqlResult::current | ( | ) | const [pure virtual] |
Returns a QSparqlResultRow containing the binding values for the current row. If the result points to a valid row (isValid() returns true), the result row is populated. An empty result row is returned when there is no result at the current position.
To retrieve just the values from a query, value() should be used since its index-based lookup is faster. Use QSparqlResultRow::binding() to retrieve the value along with meta data, such as the data type URI or language tag for literals.
| void QSparqlResult::dataReady | ( | int | totalRows | ) | [signal] |
This signal is emitted when a query has fetched data. The totalRows is the row count of the data set after the new data has arrived.
| void QSparqlResult::finished | ( | ) | [signal] |
This signal is emitted when the QSparqlResult has finished retrieving its data or when there was an error.
| bool QSparqlResult::first | ( | ) | [virtual] |
Retrieves the first row in the result, if available, and positions the query on the retrieved row. Returns true if successful. If unsuccessful the query position is set to an invalid position and false is returned.
| bool QSparqlResult::hasError | ( | ) | const |
Returns true if the query has finished and there is an error associated with the result.
| bool QSparqlResult::hasFeature | ( | QSparqlResult::Feature | feature | ) | const [virtual] |
Returns true if the QSparqlResult supports feature feature; otherwise returns false.
| bool QSparqlResult::isBool | ( | ) | const |
Returns true if the statement is an ASK query returning a boolean value
| bool QSparqlResult::isFinished | ( | ) | const [virtual] |
Returns true if the pending query has finished processing and the result has been received. If this function returns true, the hasError() and lastError() methods should return valid information.
The usage of this function differs depending on the driver, and method of execution used. For asynchronous queries the results will be available once the finished() signal has been emitted, or waitForFinished() has been called. For synchronous execution, where the driver supports QSparqlConnection::SyncExec, the value of isFinished() will be false until all the results have been retrieved using next().
E.g For a synchronous result
QSparqlResult *result = connection.syncExec(query);
// result->isFinished() will be false
while(result->next())
do something
// result->isFinished() will now be true
And for asynchronous execution
QSparqlResult *result = connection.exec(query);
result->waitForFinished();
result->isFinished(); // will be true
Note that this function only changes state if you call waitForFinished(), or if an external event happens, which in general only happens if you return to the event loop execution.
| bool QSparqlResult::isGraph | ( | ) | const |
Returns true if the statement is a CONSTRUCT or DESCRIBE query returning a graph. Each QSparqlResultRow in a graph result hasError three QSParqlBinding values, named 's', 'p' and 'o' corresponding to triples with Subject, Predicate and Object values
| bool QSparqlResult::isTable | ( | ) | const |
Returns true if this QSparqlResult object represents results that are in the tabular format, e.g., the results of a SELECT query.
| bool QSparqlResult::isValid | ( | ) | const |
Returns true if the result is positioned on a valid row (that is, the result is not positioned before the first or after the last row); otherwise returns false.
| bool QSparqlResult::last | ( | ) | [virtual] |
Retrieves the last row in the result, if available, and positions the query on the retrieved row. Note that the result must be in the finished state before calling this function or it will do nothing and return false. Returns true if successful. If unsuccessful the query position is set to an invalid position and false is returned.
| QSparqlError QSparqlResult::lastError | ( | ) | const |
Once the query has finished, returns the last error associated with the result
| bool QSparqlResult::next | ( | ) | [virtual] |
Retrieves the next row in the result, if available, and positions the query on the retrieved row. Note that the isTable() or isGraph() must return true before calling this function or it will do nothing and return false.
The following rules apply:
If the row could not be retrieved, the result is positioned after the last row and false is returned. If the row is successfully retrieved, true is returned.
| int QSparqlResult::pos | ( | ) | const |
Returns the current internal position of the query. The first row is at position zero. If the position is invalid, the function returns QSparql::BeforeFirstRow or QSparql::AfterLastRow, which are special negative values.
| bool QSparqlResult::previous | ( | ) | [virtual] |
Retrieves the previous row in the result, if available, and positions the query on the retrieved row.
The following rules apply:
If the row could not be retrieved, the result is positioned before the first row and false is returned. If the row is successfully retrieved, true is returned.
| QString QSparqlResult::query | ( | ) | const |
Returns the query which was executed for creating this QSparqlResult. Useful for debugging purposes.
| void QSparqlResult::setBoolValue | ( | bool | v | ) | [protected] |
Set the boolean result of an ASK query
| void QSparqlResult::setLastError | ( | const QSparqlError & | error | ) | [protected] |
This function is provided for derived classes to set the last error to error.
| bool QSparqlResult::setPos | ( | int | pos | ) | [virtual] |
This function is provided to set the internal (zero-based) row position to index. If the index is within the range of result rows retrieved the function returns true, otherwise false.
| void QSparqlResult::setQuery | ( | const QString & | query | ) | [protected] |
Sets the information about the query whose results this QSparqlResult object represents.
| int QSparqlResult::size | ( | ) | const [virtual] |
Returns the size of the result (number of rows returned).
A return value of -1 is used if the result does not support QuerySize information, or if the query has not yet finished (isFinished() returns false)
| QString QSparqlResult::stringValue | ( | int | i | ) | const [virtual] |
| void QSparqlResult::updatePos | ( | int | index | ) | [protected] |
This function is provided for derived classes which handle position tracking themselves, allowing them to record the current position in the results
| QVariant QSparqlResult::value | ( | int | index | ) | const [pure virtual] |
Returns the value of binding index in the current result row.
The binding values are numbered from left to right using the text of the SELECT statement. The indexes start from 0.
An invalid QVariant is returned if binding value index does not exist, if the query is inactive, or if the query is positioned on an invalid result row.
| void QSparqlResult::waitForFinished | ( | ) | [virtual] |
Suspends the execution of the calling thread until all the query results have arrived. After this function returns, isFinished() should return true, indicating the result's contents are ready to be processed.
| Copyright (C) 2010-2011 Nokia Corporation and/or its subsidiary(-ies). Commercial Qt/LGPL 2.1 with Nokia exception/GPL 3.0 |
MeeGo 1.2 Harmattan API
|