Contents

• Public Functions
• Detailed Description

Detailed Description

TheQFutureIterator class provides a Java-style const iterator forQFuture.

QFuture has bothJava-style iterators andSTL-style iterators. The Java-style iterators are more high-level and easier to use than the STL-style iterators; on the other hand, they are slightly less efficient.

An alternative to using iterators is to use index positions. SomeQFuture member functions take an index as their first parameter, making it possible to access results without using iterators.

QFutureIterator<T> allows you to iterate over aQFuture<T>. Note that there is no mutable iterator forQFuture (unlike the other Java-style iterators).

TheQFutureIterator constructor takes aQFuture as its argument. After construction, the iterator is located at the very beginning of the result list (i.e. before the first result). Here's how to iterate over all the results sequentially:

QFuture<QString> future;...QFutureIterator<QString> i(future);while (i.hasNext())qDebug()<< i.next();

Thenext() function returns the next result (waiting for it to become available, if necessary) from the future and advances the iterator. Unlike STL-style iterators, Java-style iterators pointbetween results rather than directlyat results. The first call tonext() advances the iterator to the position between the first and second result, and returns the first result; the second call tonext() advances the iterator to the position between the second and third result, and returns the second result; and so on.

Here's how to iterate over the elements in reverse order:

QFutureIterator<QString> i(future);i.toBack();while (i.hasPrevious())qDebug()<< i.previous();

If you want to find all occurrences of a particular value, usefindNext() orfindPrevious() in a loop.

Multiple iterators can be used on the same future. If the future is modified while aQFutureIterator is active, theQFutureIterator will continue iterating over the original future, ignoring the modified copy.

Member Function Documentation

QFutureIterator::QFutureIterator(constQFuture<T> & future)

Constructs an iterator for traversingfuture. The iterator is set to be at the front of the result list (before the first result).

See alsooperator=().

bool QFutureIterator::findNext(constT & value)

Searches forvalue starting from the current iterator position forward. Returns true ifvalue is found; otherwise returns false.

After the call, ifvalue was found, the iterator is positioned just after the matching result; otherwise, the iterator is positioned at the back of the result list.

See alsofindPrevious().

bool QFutureIterator::findPrevious(constT & value)

Searches forvalue starting from the current iterator position backward. Returns true ifvalue is found; otherwise returns false.

After the call, ifvalue was found, the iterator is positioned just before the matching result; otherwise, the iterator is positioned at the front of the result list.

See alsofindNext().

bool QFutureIterator::hasNext() const

Returns true if there is at least one result ahead of the iterator, e.g., the iterator isnot at the back of the result list; otherwise returns false.

See alsohasPrevious() andnext().

bool QFutureIterator::hasPrevious() const

Returns true if there is at least one result ahead of the iterator, e.g., the iterator isnot at the front of the result list; otherwise returns false.

See alsohasNext() andprevious().

constT & QFutureIterator::next()

Returns the next result and advances the iterator by one position.

Calling this function on an iterator located at the back of the result list leads to undefined results.

See alsohasNext(),peekNext(), andprevious().

constT & QFutureIterator::peekNext() const

Returns the next result without moving the iterator.

Calling this function on an iterator located at the back of the result list leads to undefined results.

See alsohasNext(),next(), andpeekPrevious().

constT & QFutureIterator::peekPrevious() const

Returns the previous result without moving the iterator.

Calling this function on an iterator located at the front of the result list leads to undefined results.

See alsohasPrevious(),previous(), andpeekNext().

constT & QFutureIterator::previous()

Returns the previous result and moves the iterator back by one position.

Calling this function on an iterator located at the front of the result list leads to undefined results.

See alsohasPrevious(),peekPrevious(), andnext().

void QFutureIterator::toBack()

Moves the iterator to the back of the result list (after the last result).

See alsotoFront() andprevious().

void QFutureIterator::toFront()

Moves the iterator to the front of the result list (before the first result).

See alsotoBack() andnext().

QFutureIterator & QFutureIterator::operator=(constQFuture<T> & future)

Makes the iterator operate onfuture. The iterator is set to be at the front of the result list (before the first result).

See alsotoFront() andtoBack().