Struct qt_core::q_map_of_int_q_variant::KeyIterator

#[repr(C)]
pub struct KeyIterator { /* fields omitted */ }

The QMap::key_iterator class provides an STL-style const iterator for QMap and QMultiMap keys.

C++ class: QMap<int, QVariant>::key_iterator.

C++ documentation:

The QMap::key_iterator class provides an STL-style const iterator for QMap and QMultiMap keys.

QMap::key_iterator is essentially the same as QMap::const_iterator with the difference that operator*() and operator->() return a key instead of a value.

For most uses QMap::iterator and QMap::const_iterator should be used, you can easily access the key by calling QMap::iterator::key():

for (QMap<int, QString>::const_iterator it = map.cbegin(), end = map.cend(); it != end; ++it) {
      cout << "The key: " << it.key() << endl
      cout << "The value: " << it.value() << endl;
      cout << "Also the value: " << (*it) << endl;
}

However, to have interoperability between QMap's keys and STL-style algorithms we need an iterator that dereferences to a key instead of a value. With QMap::key_iterator we can apply an algorithm to a range of keys without having to call QMap::keys(), which is inefficient as it costs one QMap iteration and memory allocation to create a temporary QList.

// Inefficient, keys() is expensive
QList<int> keys = map.keys();
int numPrimes = std::count_if(map.cbegin(), map.cend(), isPrimeNumber);
qDeleteAll(map2.keys());
// Efficient, no memory allocation needed
int numPrimes = std::count_if(map.keyBegin(), map.keyEnd(), isPrimeNumber);
qDeleteAll(map2.keyBegin(), map2.keyEnd());

QMap::key_iterator is const, it's not possible to modify the key.

The default QMap::key_iterator constructor creates an uninitialized iterator. You must initialize it using a QMap function like QMap::keyBegin() or QMap::keyEnd().

Warning: Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read Implicit sharing iterator problem.

Methods

impl KeyIterator

pub unsafe fn base(&self) -> CppBox<ConstIterator>

Returns the underlying const_iterator this key_iterator is based on.

Calls C++ function: QMap<int, QVariant>::const_iterator QMap<int, QVariant>::key_iterator::base() const.

C++ documentation:

Returns the underlying const_iterator this key_iterator is based on.

pub unsafe fn copy_from(
    &mut self,
    other: impl CastInto<Ref<KeyIterator>>
) -> MutRef<KeyIterator>

The QMap::key_iterator class provides an STL-style const iterator for QMap and QMultiMap keys.

Calls C++ function: QMap<int, QVariant>::key_iterator& QMap<int, QVariant>::key_iterator::operator=(const QMap<int, QVariant>::key_iterator& other).

C++ documentation:

The QMap::key_iterator class provides an STL-style const iterator for QMap and QMultiMap keys.

QMap::key_iterator is essentially the same as QMap::const_iterator with the difference that operator*() and operator->() return a key instead of a value.

For most uses QMap::iterator and QMap::const_iterator should be used, you can easily access the key by calling QMap::iterator::key():

for (QMap<int, QString>::const_iterator it = map.cbegin(), end = map.cend(); it != end; ++it) {
      cout << "The key: " << it.key() << endl
      cout << "The value: " << it.value() << endl;
      cout << "Also the value: " << (*it) << endl;
}

However, to have interoperability between QMap's keys and STL-style algorithms we need an iterator that dereferences to a key instead of a value. With QMap::key_iterator we can apply an algorithm to a range of keys without having to call QMap::keys(), which is inefficient as it costs one QMap iteration and memory allocation to create a temporary QList.

// Inefficient, keys() is expensive
QList<int> keys = map.keys();
int numPrimes = std::count_if(map.cbegin(), map.cend(), isPrimeNumber);
qDeleteAll(map2.keys());
// Efficient, no memory allocation needed
int numPrimes = std::count_if(map.keyBegin(), map.keyEnd(), isPrimeNumber);
qDeleteAll(map2.keyBegin(), map2.keyEnd());

QMap::key_iterator is const, it's not possible to modify the key.

The default QMap::key_iterator constructor creates an uninitialized iterator. You must initialize it using a QMap function like QMap::keyBegin() or QMap::keyEnd().

Warning: Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read Implicit sharing iterator problem.

pub unsafe fn dec(&mut self) -> MutRef<KeyIterator>

The prefix -- operator (--i) makes the preceding item current and returns an iterator pointing to the new current item.

Calls C++ function: QMap<int, QVariant>::key_iterator& QMap<int, QVariant>::key_iterator::operator--().

C++ documentation:

The prefix -- operator (--i) makes the preceding item current and returns an iterator pointing to the new current item.

Calling this function on QHash::keyBegin() leads to undefined results.

See also operator++().

pub unsafe fn dec_postfix(&mut self, arg1: c_int) -> CppBox<KeyIterator>

This is an overloaded function.

Calls C++ function: QMap<int, QVariant>::key_iterator QMap<int, QVariant>::key_iterator::operator--(int arg1).

C++ documentation:

This is an overloaded function.

The postfix -- operator (i--) makes the preceding item current and returns an iterator pointing to the previous item.

pub unsafe fn inc(&mut self) -> MutRef<KeyIterator>

The prefix ++ operator (++i) advances the iterator to the next item in the hash and returns an iterator to the new current item.

Calls C++ function: QMap<int, QVariant>::key_iterator& QMap<int, QVariant>::key_iterator::operator++().

C++ documentation:

The prefix ++ operator (++i) advances the iterator to the next item in the hash and returns an iterator to the new current item.

Calling this function on QHash::keyEnd() leads to undefined results.

See also operator--().

pub unsafe fn inc_postfix(&mut self, arg1: c_int) -> CppBox<KeyIterator>

This is an overloaded function.

Calls C++ function: QMap<int, QVariant>::key_iterator QMap<int, QVariant>::key_iterator::operator++(int arg1).

C++ documentation:

This is an overloaded function.

The postfix ++ operator (i++) advances the iterator to the next item in the hash and returns an iterator to the previous item.

pub unsafe fn indirection(&self) -> Ref<c_int>

Returns the current item's key.

Calls C++ function: const int& QMap<int, QVariant>::key_iterator::operator*() const.

C++ documentation:

Returns the current item's key.

pub unsafe fn new_0a() -> CppBox<KeyIterator>

Default constructs an instance of key_iterator.

Calls C++ function: [constructor] void QMap<int, QVariant>::key_iterator::key_iterator().

C++ documentation:

Default constructs an instance of key_iterator.

pub unsafe fn new_1a(
    o: impl CastInto<Ref<ConstIterator>>
) -> CppBox<KeyIterator>

Calls C++ function: [constructor] void QMap<int, QVariant>::key_iterator::key_iterator(QMap<int, QVariant>::const_iterator o).

pub unsafe fn new_copy(
    other: impl CastInto<Ref<KeyIterator>>
) -> CppBox<KeyIterator>

The QMap::key_iterator class provides an STL-style const iterator for QMap and QMultiMap keys.

Calls C++ function: [constructor] void QMap<int, QVariant>::key_iterator::key_iterator(const QMap<int, QVariant>::key_iterator& other).

C++ documentation:

The QMap::key_iterator class provides an STL-style const iterator for QMap and QMultiMap keys.

QMap::key_iterator is essentially the same as QMap::const_iterator with the difference that operator*() and operator->() return a key instead of a value.

For most uses QMap::iterator and QMap::const_iterator should be used, you can easily access the key by calling QMap::iterator::key():

for (QMap<int, QString>::const_iterator it = map.cbegin(), end = map.cend(); it != end; ++it) {
      cout << "The key: " << it.key() << endl
      cout << "The value: " << it.value() << endl;
      cout << "Also the value: " << (*it) << endl;
}

However, to have interoperability between QMap's keys and STL-style algorithms we need an iterator that dereferences to a key instead of a value. With QMap::key_iterator we can apply an algorithm to a range of keys without having to call QMap::keys(), which is inefficient as it costs one QMap iteration and memory allocation to create a temporary QList.

// Inefficient, keys() is expensive
QList<int> keys = map.keys();
int numPrimes = std::count_if(map.cbegin(), map.cend(), isPrimeNumber);
qDeleteAll(map2.keys());
// Efficient, no memory allocation needed
int numPrimes = std::count_if(map.keyBegin(), map.keyEnd(), isPrimeNumber);
qDeleteAll(map2.keyBegin(), map2.keyEnd());

QMap::key_iterator is const, it's not possible to modify the key.

The default QMap::key_iterator constructor creates an uninitialized iterator. You must initialize it using a QMap function like QMap::keyBegin() or QMap::keyEnd().

Warning: Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read Implicit sharing iterator problem.

pub unsafe fn struct_deref(&self) -> Ptr<c_int>

Returns a pointer to the current item's key.

Calls C++ function: const int* QMap<int, QVariant>::key_iterator::operator->() const.

C++ documentation:

Returns a pointer to the current item's key.

Trait Implementations

impl PartialEq<Ref<KeyIterator>> for KeyIterator

fn eq(&self, o: &Ref<KeyIterator>) -> bool

Returns true if other points to the same item as this iterator; otherwise returns false.

Calls C++ function: bool QMap<int, QVariant>::key_iterator::operator==(QMap<int, QVariant>::key_iterator o) const.

C++ documentation:

Returns true if other points to the same item as this iterator; otherwise returns false.

See also operator!=().

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl CppDeletable for KeyIterator

unsafe fn delete(&mut self)

The QMap::key_iterator class provides an STL-style const iterator for QMap and QMultiMap keys.

Calls C++ function: [destructor] void QMap<int, QVariant>::key_iterator::~key_iterator().

C++ documentation:

The QMap::key_iterator class provides an STL-style const iterator for QMap and QMultiMap keys.

QMap::key_iterator is essentially the same as QMap::const_iterator with the difference that operator*() and operator->() return a key instead of a value.

For most uses QMap::iterator and QMap::const_iterator should be used, you can easily access the key by calling QMap::iterator::key():

for (QMap<int, QString>::const_iterator it = map.cbegin(), end = map.cend(); it != end; ++it) {
      cout << "The key: " << it.key() << endl
      cout << "The value: " << it.value() << endl;
      cout << "Also the value: " << (*it) << endl;
}

However, to have interoperability between QMap's keys and STL-style algorithms we need an iterator that dereferences to a key instead of a value. With QMap::key_iterator we can apply an algorithm to a range of keys without having to call QMap::keys(), which is inefficient as it costs one QMap iteration and memory allocation to create a temporary QList.

// Inefficient, keys() is expensive
QList<int> keys = map.keys();
int numPrimes = std::count_if(map.cbegin(), map.cend(), isPrimeNumber);
qDeleteAll(map2.keys());
// Efficient, no memory allocation needed
int numPrimes = std::count_if(map.keyBegin(), map.keyEnd(), isPrimeNumber);
qDeleteAll(map2.keyBegin(), map2.keyEnd());

QMap::key_iterator is const, it's not possible to modify the key.

The default QMap::key_iterator constructor creates an uninitialized iterator. You must initialize it using a QMap function like QMap::keyBegin() or QMap::keyEnd().

Warning: Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read Implicit sharing iterator problem.

impl Decrement for KeyIterator

type Output = MutRef<KeyIterator>

Output type.

unsafe fn dec(&mut self) -> MutRef<KeyIterator>

The prefix -- operator (--i) makes the preceding item current and returns an iterator pointing to the new current item.

Calls C++ function: QMap<int, QVariant>::key_iterator& QMap<int, QVariant>::key_iterator::operator--().

C++ documentation:

The prefix -- operator (--i) makes the preceding item current and returns an iterator pointing to the new current item.

Calling this function on QHash::keyBegin() leads to undefined results.

See also operator++().

impl Increment for KeyIterator

type Output = MutRef<KeyIterator>

Output type.

unsafe fn inc(&mut self) -> MutRef<KeyIterator>

The prefix ++ operator (++i) advances the iterator to the next item in the hash and returns an iterator to the new current item.

Calls C++ function: QMap<int, QVariant>::key_iterator& QMap<int, QVariant>::key_iterator::operator++().

C++ documentation:

The prefix ++ operator (++i) advances the iterator to the next item in the hash and returns an iterator to the new current item.

Calling this function on QHash::keyEnd() leads to undefined results.

See also operator--().

impl Indirection for KeyIterator

type Output = Ref<c_int>

Output type.

unsafe fn indirection(&self) -> Ref<c_int>

Returns the current item's key.

Calls C++ function: const int& QMap<int, QVariant>::key_iterator::operator*() const.

C++ documentation:

Returns the current item's key.