qtconcurrentfilter

\title Concurrent Filter and Filter-Reduce

Selecting values from a sequence and combining them, all in parallel.

The QtConcurrent::filter(), QtConcurrent::filtered() and QtConcurrent::filteredReduced() functions filter items in a sequence such as a QList in parallel. QtConcurrent::filter() modifies a sequence in-place, QtConcurrent::filtered() returns a new sequence containing the filtered content, and QtConcurrent::filteredReduced() returns a single result.

These functions are part of the \l {Qt Concurrent} framework.

Each of the above functions have a blocking variant that returns the final result instead of a QFuture. You use them in the same way as the asynchronous variants.

QStringList strings = ...;
 
// each call blocks until the entire operation is finished
QStringList lowerCaseStrings = QtConcurrent::blockingFiltered(strings, allLowerCase);
 
 
QtConcurrent::blockingFilter(strings, allLowerCase);
 
QSet<QString> dictionary = QtConcurrent::blockingFilteredReduced(strings, allLowerCase, addToDictionary);

Note that the result types above are not QFuture objects, but real result types (in this case, QStringList and QSet<QString>).