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QAssociativeIterable 类

QAssociativeIterable 类是关联容器的可迭代接口，在 QVariant . 更多...

头： #include <QAssociativeIterable>
CMake: find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake: QT += core
继承： QIterable

公共类型

BidirectionalConstIterator
BidirectionalIterator
ForwardConstIterator
ForwardIterator
InputConstIterator
InputIterator
RandomAccessConstIterator
RandomAccessIterator
const_iterator
iterator

公共函数

bool containsKey (const QVariant & key )
QAssociativeIterable::const_iterator find (const QVariant & key ) const
void insertKey (const QVariant & key )
QAssociativeIterable::iterator mutableFind (const QVariant & key )
void removeKey (const QVariant & key )
void setValue (const QVariant & key , const QVariant & mapped )
QVariant value (const QVariant & key ) const

详细描述

此类允许一些方法访问关联容器的元素，保持在 QVariant 。可以提取 QAssociativeIterable 的实例，从 QVariant if it can be converted to a QVariantHash or QVariantMap or if a custom mutable view has been registered. 

QHash<int, QString> mapping;
mapping.insert(7, "Seven");
mapping.insert(11, "Eleven");
mapping.insert(42, "Forty-two");
QVariant variant = QVariant::fromValue(mapping);
if (variant.canConvert<QVariantHash>()) {
    QAssociativeIterable iterable = variant.value<QAssociativeIterable>();
    // Can use foreach over the values:
    foreach (const QVariant &v, iterable) {
        qDebug() << v;
    }
    // Can use C++11 range-for over the values:
    for (const QVariant &v : iterable) {
        qDebug() << v;
    }
    // Can use iterators:
    QAssociativeIterable::const_iterator it = iterable.begin();
    const QAssociativeIterable::const_iterator end = iterable.end();
    for ( ; it != end; ++it) {
        qDebug() << *it; // The current value
        qDebug() << it.key();
        qDebug() << it.value();
    }
}

容器本身不会被拷贝，在遍历它之前。

另请参阅 QVariant .

成员类型文档编制

[alias] QAssociativeIterable:: BidirectionalConstIterator

Exposes a const_iterator using std::bidirectional_iterator_tag.

[alias] QAssociativeIterable:: BidirectionalIterator

Exposes an iterator using std::bidirectional_iterator_tag.

[alias] QAssociativeIterable:: ForwardConstIterator

Exposes a const_iterator using std::forward_iterator_tag.

[alias] QAssociativeIterable:: ForwardIterator

Exposes an iterator using std::forward_iterator_tag.

[alias] QAssociativeIterable:: InputConstIterator

Exposes a const_iterator using std::input_iterator_tag.

[alias] QAssociativeIterable:: InputIterator

Exposes an iterator using std::input_iterator_tag.

[alias] QAssociativeIterable:: RandomAccessConstIterator

Exposes a const_iterator using std::random_access_iterator_tag.

[alias] QAssociativeIterable:: RandomAccessIterator

Exposes an iterator using std::random_access_iterator_tag.

[alias] QAssociativeIterable:: const_iterator

The QAssociativeIterable::const_iterator allows iteration over a container in a QVariant .

A QAssociativeIterable::const_iterator can only be created by a QAssociativeIterable instance, and can be used in a way similar to other stl-style iterators. 

QHash<int, QString> mapping;
mapping.insert(7, "Seven");
mapping.insert(11, "Eleven");
mapping.insert(42, "Forty-two");
QVariant variant = QVariant::fromValue(mapping);
if (variant.canConvert<QVariantHash>()) {
    QAssociativeIterable iterable = variant.value<QAssociativeIterable>();
    // Can use foreach over the values:
    foreach (const QVariant &v, iterable) {
        qDebug() << v;
    }
    // Can use C++11 range-for over the values:
    for (const QVariant &v : iterable) {
        qDebug() << v;
    }
    // Can use iterators:
    QAssociativeIterable::const_iterator it = iterable.begin();
    const QAssociativeIterable::const_iterator end = iterable.end();
    for ( ; it != end; ++it) {
        qDebug() << *it; // The current value
        qDebug() << it.key();
        qDebug() << it.value();
    }
}

另请参阅 QAssociativeIterable .

[alias, since 6.0] QAssociativeIterable:: iterator

The QAssociativeIterable::iterator allows iteration over a container in a QVariant .

A QAssociativeIterable::iterator can only be created by a QAssociativeIterable instance, and can be used in a way similar to other stl-style iterators.

This typedef was introduced in Qt 6.0.

另请参阅 QAssociativeIterable .

成员函数文档编制

bool QAssociativeIterable:: containsKey (const QVariant & key )

返回 true if the container has an entry with the given key ，或 false otherwise. If the key isn't convertible to the expected type, false 被返回。

QAssociativeIterable::const_iterator QAssociativeIterable:: find (const QVariant & key ) const

Retrieves a const_iterator pointing to the element at the given key , or the end of the container if that key does not exist. If the key isn't convertible to the expected type, the end of the container is returned.

void QAssociativeIterable:: insertKey (const QVariant & key )

Inserts a new entry with the given key , or resets the mapped value of any existing entry with the given key to the default constructed mapped value. The key is coerced to the expected type: If it isn't convertible, a default value is inserted.

QAssociativeIterable::iterator QAssociativeIterable:: mutableFind (const QVariant & key )

Retrieves an iterator pointing to the element at the given key , or the end of the container if that key does not exist. If the key isn't convertible to the expected type, the end of the container is returned.

void QAssociativeIterable:: removeKey (const QVariant & key )

Removes the entry with the given key from the container. The key is coerced to the expected type: If it isn't convertible, the default value is removed.

void QAssociativeIterable:: setValue (const QVariant & key , const QVariant & mapped )

Sets the mapped value associated with key to mapped , if possible. Inserts a new entry if none exists yet, for the given key 。若 key is not convertible to the key type, the value for the default-constructed key type is overwritten.

另请参阅 value ().

QVariant QAssociativeIterable:: value (const QVariant & key ) const

Retrieves the mapped value at the given key , or a default-constructed QVariant of the mapped type, if the key does not exist. If the key is not convertible to the key type, the mapped value associated with the default-constructed key is returned.

另请参阅 setValue ().

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