- Qt 6.9
- Qt Core
- C++ Classes
- QMetaSequence
- Qt 6.9.3 Reference Documentation

# QMetaSequence Class

The QMetaSequence class allows type erased access to sequential containers. More...

Header: | `#include <QMetaSequence>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Core)` `target_link_libraries(mytarget PRIVATE Qt6::Core)`
qmake: | `QT += core`
Since: | Qt 6.0
Inherits: | QMetaContainer

- List of all members, including inherited members

This class is equality-comparable.

## Public Functions

void | addValue(void *container, const void *value) const
void | addValueAtBegin(void *container, const void *value) const
void | addValueAtEnd(void *container, const void *value) const
bool | canAddValue() const
bool | canAddValueAtBegin() const
bool | canAddValueAtEnd() const
bool | canEraseRangeAtIterator() const
bool | canEraseValueAtIterator() const
bool | canGetValueAtConstIterator() const
bool | canGetValueAtIndex() const
bool | canGetValueAtIterator() const
bool | canInsertValueAtIterator() const
bool | canRemoveValue() const
bool | canRemoveValueAtBegin() const
bool | canRemoveValueAtEnd() const
bool | canSetValueAtIndex() const
bool | canSetValueAtIterator() const
void | eraseRangeAtIterator(void *container, const void *iterator1, const void *iterator2) const
void | eraseValueAtIterator(void *container, const void *iterator) const
void | insertValueAtIterator(void *container, const void *iterator, const void *value) const
bool | isSortable() const
void | removeValue(void *container) const
void | removeValueAtBegin(void *container) const
void | removeValueAtEnd(void *container) const
void | setValueAtIndex(void *container, qsizetype index, const void *value) const
void | setValueAtIterator(const void *iterator, const void *value) const
void | valueAtConstIterator(const void *iterator, void *result) const
void | valueAtIndex(const void *container, qsizetype index, void *result) const
void | valueAtIterator(const void *iterator, void *result) const
QMetaType | valueMetaType() const

## Static Public Members

`(since 6.0)` QMetaSequence | fromContainer()

## Related Non-Members

`(since 6.0)` bool | operator!=(const QMetaSequence &lhs, const QMetaSequence &rhs)
`(since 6.0)` bool | operator==(const QMetaSequence &lhs, const QMetaSequence &rhs)

## Detailed Description

The class provides a number of primitive container operations, using void* as operands. This way, you can manipulate a generic container retrieved from a Variant without knowing its type.

The void* arguments to the various methods are typically created by using a QVariant of the respective container or value type, and calling its QVariant::data() or QVariant::constData() methods. However, you can also pass plain pointers to objects of the container or value type.

Iterator invalidation follows the rules given by the underlying containers and is not expressed in the API. Therefore, for a truly generic container, any iterators should be considered invalid after any write operation.

## Member Function Documentation

### void QMetaSequence::addValue(void *container, const void *value) const

Adds value to the container if possible. If canAddValue() returns `false`, the value is not added. Else, if canAddValueAtEnd() returns `true`, the value is added to the end of the container. Else, if canAddValueAtBegin() returns `true`, the value is added to the beginning of the container. Else, the value is added in an unspecified place or not at all. The latter is the case for adding values to an unordered container, for example QSet.

See also canAddValue(), canAddValueAtBegin(), canAddValueAtEnd(), isSortable(), and removeValue().

### void QMetaSequence::addValueAtBegin(void *container, const void *value) const

Adds value to the beginning of container if possible. If canAddValueAtBegin() returns `false`, the value is not added.

See also canAddValueAtBegin(), isSortable(), and removeValueAtBegin().

### void QMetaSequence::addValueAtEnd(void *container, const void *value) const

Adds value to the end of container if possible. If canAddValueAtEnd() returns `false`, the value is not added.

See also canAddValueAtEnd(), isSortable(), and removeValueAtEnd().

### bool QMetaSequence::canAddValue() const

Returns `true` if values can be added to the container, `false` otherwise.

See also addValue() and isSortable().

### bool QMetaSequence::canAddValueAtBegin() const

Returns `true` if values added using addValue() can be placed at the beginning of the container, otherwise returns `false`.

See also addValueAtBegin() and canAddValueAtEnd().

### bool QMetaSequence::canAddValueAtEnd() const

Returns `true` if values added using addValue() can be placed at the end of the container, otherwise returns `false`.

See also addValueAtEnd() and canAddValueAtBegin().

### bool QMetaSequence::canEraseRangeAtIterator() const

Returns `true` if a range between two iterators can be erased from the container, `false` otherwise.

### bool QMetaSequence::canEraseValueAtIterator() const

Returns `true` if the value pointed to by a non-const iterator can be erased, `false` otherwise.

See also hasIterator() and eraseValueAtIterator().

### bool QMetaSequence::canGetValueAtConstIterator() const

Returns `true` if the underlying container can retrieve the value pointed to by a const iterator, `false` otherwise.

See also hasConstIterator() and valueAtConstIterator().

### bool QMetaSequence::canGetValueAtIndex() const

Returns `true` if values can be retrieved from the container by index, otherwise `false`.

See also valueAtIndex().

### bool QMetaSequence::canGetValueAtIterator() const

Returns `true` if the underlying container can retrieve the value pointed to by a non-const iterator, `false` otherwise.

See also hasIterator() and valueAtIterator().

### bool QMetaSequence::canInsertValueAtIterator() const

Returns `true` if the underlying container can insert a new value, taking the location pointed to by a non-const iterator into account.

See also hasIterator() and insertValueAtIterator().

### bool QMetaSequence::canRemoveValue() const

Returns `true` if values can be removed from the container, `false` otherwise.

See also removeValue() and isSortable().

### bool QMetaSequence::canRemoveValueAtBegin() const

Returns `true` if values can be removed from the beginning of the container using removeValue(), otherwise returns `false`.

See also removeValueAtBegin() and canRemoveValueAtEnd().

### bool QMetaSequence::canRemoveValueAtEnd() const

Returns `true` if values can be removed from the end of the container using removeValue(), otherwise returns `false`.

See also removeValueAtEnd() and canRemoveValueAtBegin().

### bool QMetaSequence::canSetValueAtIndex() const

Returns `true` if a value can be written to the container by index, otherwise `false`.

See also setValueAtIndex().

### bool QMetaSequence::canSetValueAtIterator() const

Returns `true` if the underlying container can write to the value pointed to by a non-const iterator, `false` otherwise.

See also hasIterator() and setValueAtIterator().

### void QMetaSequence::eraseRangeAtIterator(void *container, const void *iterator1, const void *iterator2) const

Erases the range of values between the iterators iterator1 and iterator2 from the container, if possible.

See also canEraseValueAtIterator(), begin(), and end().

### void QMetaSequence::eraseValueAtIterator(void *container, const void *iterator) const

Erases the value pointed to by the non-const iterator from the container, if possible.

See also canEraseValueAtIterator(), begin(), and end().

### `[static constexpr, since 6.0]` template <typename T> QMetaSequence QMetaSequence::fromContainer()

Returns the QMetaSequence corresponding to the type given as template parameter.

This function was introduced in Qt 6.0.

### void QMetaSequence::insertValueAtIterator(void *container, const void *iterator, const void *value) const

Inserts value into the container, if possible, taking the non-const iterator into account. If canInsertValueAtIterator() returns `false`, the value is not inserted. Else if isSortable() returns `true`, the value is inserted before the value pointed to by iterator. Else, the value is inserted at an unspecified place or not at all. In the latter case, the iterator is taken as a hint. If it points to the correct place for the value, the operation may be faster than a addValue() without iterator.

See also canInsertValueAtIterator(), isSortable(), begin(), and end().

### bool QMetaSequence::isSortable() const

Returns `true` if the underlying container is sortable, otherwise returns `false`. A container is considered sortable if values added to it are placed in a defined location. Inserting into or adding to a sortable container will always succeed. Inserting into or adding to an unsortable container may not succeed, for example if the container is a QSet that already contains the value being inserted.

See also addValue(), insertValueAtIterator(), canAddValueAtBegin(), canAddValueAtEnd(), canRemoveValueAtBegin(), and canRemoveValueAtEnd().

### void QMetaSequence::removeValue(void *container) const

Removes a value from the container if possible. If canRemoveValue() returns `false`, no value is removed. Else, if canRemoveValueAtEnd() returns `true`, the last value in the container is removed. Else, if canRemoveValueAtBegin() returns `true`, the first value in the container is removed. Else, an unspecified value or nothing is removed.

See also canRemoveValue(), canRemoveValueAtBegin(), canRemoveValueAtEnd(), isSortable(), and addValue().

### void QMetaSequence::removeValueAtBegin(void *container) const

Removes a value from the beginning of container if possible. If canRemoveValueAtBegin() returns `false`, the value is not removed.

See also canRemoveValueAtBegin(), isSortable(), and addValueAtBegin().

### void QMetaSequence::removeValueAtEnd(void *container) const

Removes a value from the end of container if possible. If canRemoveValueAtEnd() returns `false`, the value is not removed.

See also canRemoveValueAtEnd(), isSortable(), and addValueAtEnd().

### void QMetaSequence::setValueAtIndex(void *container, qsizetype index, const void *value) const

Overwrites the value at index in the container using the value passed as parameter if that is possible.

See also valueAtIndex() and canSetValueAtIndex().

### void QMetaSequence::setValueAtIterator(const void *iterator, const void *value) const

Writes value to the value pointed to by the non-const iterator, if possible.

See also valueAtIterator(), canSetValueAtIterator(), begin(), and end().

### void QMetaSequence::valueAtConstIterator(const void *iterator, void *result) const

Retrieves the value pointed to by the const iterator and stores it in the memory location pointed to by result, if possible.

See also canGetValueAtConstIterator(), constBegin(), and constEnd().

### void QMetaSequence::valueAtIndex(const void *container, qsizetype index, void *result) const

Retrieves the value at index in the container and places it in the memory location pointed to by result, if that is possible.

See also setValueAtIndex() and canGetValueAtIndex().

### void QMetaSequence::valueAtIterator(const void *iterator, void *result) const

Retrieves the value pointed to by the non-const iterator and stores it in the memory location pointed to by result, if possible.

See also setValueAtIterator(), canGetValueAtIterator(), begin(), and end().

### QMetaType QMetaSequence::valueMetaType() const

Returns the meta type for values stored in the container.

## Related Non-Members

### `[noexcept, since 6.0]` bool operator!=(const QMetaSequence &lhs, const QMetaSequence &rhs)

Returns `true` if the QMetaSequence lhs represents a different container type than the QMetaSequence rhs, otherwise returns `false`.

This function was introduced in Qt 6.0.

### `[noexcept, since 6.0]` bool operator==(const QMetaSequence &lhs, const QMetaSequence &rhs)

Returns `true` if the QMetaSequence lhs represents the same container type as the QMetaSequence rhs, otherwise returns `false`.

This function was introduced in Qt 6.0.