内容

• 公共类型
• 公共函数
• 静态公共成员
• 相关非成员
• 详细描述

QSet 类

QSet class is a template class that provides a hash-table-based set. 更多...

头：	#include <QSet>
qmake:	QT += core

• 所有成员列表，包括继承成员

注意： 此类的所有函数 可重入 .

公共类型

class	const_iterator
class	iterator
typedef	ConstIterator
typedef	Iterator
typedef	const_pointer
typedef	const_reference
typedef	const_reverse_iterator
typedef	difference_type
typedef	key_type
typedef	pointer
typedef	reference
typedef	reverse_iterator
typedef	size_type
typedef	value_type

公共函数

	QSet ()
	QSet (std::initializer_list<T> list )
const_iterator	begin () const
iterator	begin ()
int	capacity () const
const_iterator	cbegin () const
const_iterator	cend () const
void	clear ()
const_iterator	constBegin () const
const_iterator	constEnd () const
const_iterator	constFind (const T & value ) const
bool	contains (const T & value ) const
bool	contains (const QSet<T> & other ) const
int	count () const
const_reverse_iterator	crbegin () const
const_reverse_iterator	crend () const
bool	empty () const
const_iterator	end () const
iterator	end ()
iterator	erase (const_iterator pos )
iterator	erase (iterator pos )
const_iterator	find (const T & value ) const
iterator	find (const T & value )
iterator	insert (const T & value )
QSet<T> &	intersect (const QSet<T> & other )
bool	intersects (const QSet<T> & other ) const
bool	isEmpty () const
reverse_iterator	rbegin ()
const_reverse_iterator	rbegin () const
bool	remove (const T & value )
reverse_iterator	rend ()
const_reverse_iterator	rend () const
void	reserve (int size )
int	size () const
void	squeeze ()
QSet<T> &	subtract (const QSet<T> & other )
void	swap (QSet<T> & other )
QList<T>	toList () const
QSet<T> &	unite (const QSet<T> & other )
QList<T>	values () const
bool	operator!= (const QSet<T> & other ) const
QSet<T>	operator& (const QSet<T> & other ) const
QSet<T> &	operator&= (const QSet<T> & other )
QSet<T> &	operator&= (const T & value )
QSet<T>	operator+ (const QSet<T> & other ) const
QSet<T> &	operator+= (const QSet<T> & other )
QSet<T> &	operator+= (const T & value )
QSet<T>	operator- (const QSet<T> & other ) const
QSet<T> &	operator-= (const QSet<T> & other )
QSet<T> &	operator-= (const T & value )
QSet<T> &	operator<< (const T & value )
bool	operator== (const QSet<T> & other ) const
QSet<T>	operator| (const QSet<T> & other ) const
QSet<T> &	operator|= (const QSet<T> & other )
QSet<T> &	operator|= (const T & value )

静态公共成员

QSet<T>

fromList (const QList<T> & list )

相关非成员

QDataStream &	operator<< (QDataStream & out , const QSet<T> & set )
QDataStream &	operator>> (QDataStream & in , QSet<T> & set )

详细描述

QSet class is a template class that provides a hash-table-based set.

QSet <T> is one of Qt's generic 容器类 . It stores values in an unspecified order and provides very fast lookup of the values. Internally, QSet <T> is implemented as a QHash .

这里是范例 QSet with QString 值：

QSet<QString> set;
					

要将值插入集，使用 insert ():

set.insert("one");
set.insert("three");
set.insert("seven");
					

将项插入集的另一方式是使用 operator<<()：

set << "twelve" << "fifteen" << "nineteen";
					

要测试项是否属于集，使用 contains ():

if (!set.contains("ninety-nine"))
    ...
					

If you want to navigate through all the values stored in a QSet , you can use an iterator. QSet supports both Java 样式迭代器 ( QSetIterator and QMutableSetIterator ) and STL 样式迭代器 ( QSet::iterator and QSet::const_iterator ). Here's how to iterate over a QSet < QWidget *> using a Java-style iterator:

QSetIterator<QWidget *> i(set);
while (i.hasNext())
    qDebug() << i.next();
					

Here's the same code, but using an STL-style iterator:

QSet<QWidget *>::const_iterator i = set.constBegin();
while (i != set.constEnd()) {
    qDebug() << *i;
    ++i;
}
					

QSet is unordered, so an iterator's sequence cannot be assumed to be predictable. If ordering by key is required, use a QMap .

To navigate through a QSet , you can also use foreach :

QSet<QString> set;
...
foreach (const QString &value, set)
    qDebug() << value;
					

Items can be removed from the set using remove (). There is also a clear () function that removes all items.

QSet 's value data type must be an 可赋值数据类型 . You cannot, for example, store a QWidget as a value; instead, store a QWidget *. In addition, the type must provide operator==() , and there must also be a global qHash () function that returns a hash value for an argument of the key's type. See the QHash documentation for a list of types supported by qHash ().

在内部， QSet uses a hash table to perform lookups. The hash table automatically grows and shrinks to provide fast lookups without wasting memory. You can still control the size of the hash table by calling reserve (), if you already know approximately how many elements the QSet will contain, but this isn't necessary to obtain good performance. You can also call capacity () to retrieve the hash table's size.

另请参阅 QSetIterator , QMutableSetIterator , QHash ，和 QMap .

成员类型文档编制

typedef QSet:: ConstIterator

Qt 样式同义词 QSet::const_iterator .

typedef QSet:: Iterator

Qt 样式同义词 QSet::iterator .

该 typedef 在 Qt 4.2 引入。

typedef QSet:: const_pointer

Typedef for const T *. Provided for STL compatibility.

typedef QSet:: const_reference

Typedef for const T &. Provided for STL compatibility.

typedef QSet:: const_reverse_iterator

The QSet::const_reverse_iterator typedef provides an STL-style const reverse iterator for QSet .

It is simply a typedef for std::reverse_iterator<QSet::const_iterator> .

警告： 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 隐式共享迭代器问题 .

该 typedef 在 Qt 5.6 引入。

另请参阅 QSet::rbegin (), QSet::rend (), QSet::reverse_iterator ，和 QSet::const_iterator .

typedef QSet:: difference_type

Typedef for const ptrdiff_t. Provided for STL compatibility.

typedef QSet:: key_type

Typedef for T. Provided for STL compatibility.

typedef QSet:: pointer

Typedef for T *. Provided for STL compatibility.

typedef QSet:: reference

Typedef for T &. Provided for STL compatibility.

typedef QSet:: reverse_iterator

The QSet::reverse_iterator typedef provides an STL-style non-const reverse iterator for QSet .

It is simply a typedef for std::reverse_iterator<QSet::iterator> .

警告： 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 隐式共享迭代器问题 .

该 typedef 在 Qt 5.6 引入。

另请参阅 QSet::rbegin (), QSet::rend (), QSet::const_reverse_iterator ，和 QSet::iterator .

typedef QSet:: size_type

Typedef for int. Provided for STL compatibility.

typedef QSet:: value_type

Typedef for T. Provided for STL compatibility.

成员函数文档编制

QSet:: QSet ()

构造空集。

另请参阅 clear ().

QSet:: QSet ( std::initializer_list < T > list )

Constructs a set with a copy of each of the elements in the initializer list list .

This function is only available if the program is being compiled in C++11 mode.

该函数在 Qt 5.1 引入。

const_iterator QSet:: begin () const

返回常量 STL 样式迭代器 positioned at the first item in the set.

另请参阅 constBegin () 和 end ().

iterator QSet:: begin ()

这是重载函数。

Returns a non-const STL 样式迭代器 positioned at the first item in the set.

该函数在 Qt 4.2 引入。

int QSet:: capacity () const

Returns the number of buckets in the set's internal hash table.

The sole purpose of this function is to provide a means of fine tuning QSet 's memory usage. In general, you will rarely ever need to call this function. If you want to know how many items are in the set, call size ().

另请参阅 reserve () 和 squeeze ().

const_iterator QSet:: cbegin () const

返回常量 STL 样式迭代器 positioned at the first item in the set.

该函数在 Qt 5.0 引入。

另请参阅 begin () 和 cend ().

const_iterator QSet:: cend () const

返回常量 STL 样式迭代器 pointing to the imaginary item after the last item in the set.

该函数在 Qt 5.0 引入。

另请参阅 cbegin () 和 end ().

void QSet:: clear ()

从集移除所有元素。

另请参阅 remove ().

const_iterator QSet:: constBegin () const

返回常量 STL 样式迭代器 positioned at the first item in the set.

另请参阅 begin () 和 constEnd ().

const_iterator QSet:: constEnd () const

返回常量 STL 样式迭代器 pointing to the imaginary item after the last item in the set.

另请参阅 constBegin () 和 end ().

const_iterator QSet:: constFind (const T & value ) const

Returns a const iterator positioned at the item value in the set. If the set contains no item value , the function returns constEnd ().

该函数在 Qt 4.2 引入。

另请参阅 find () 和 contains ().

bool QSet:: contains (const T & value ) const

返回 true 若集包含项 value ；否则返回 false。

另请参阅 insert (), remove ()，和 find ().

bool QSet:: contains (const QSet < T > & other ) const

返回 true 若集包含的所有项来自 other 集；否则返回 false .

该函数在 Qt 4.6 引入。

另请参阅 insert (), remove ()，和 find ().

int QSet:: count () const

如同 size ().

const_reverse_iterator QSet:: crbegin () const

返回常量 STL-style reverse iterator pointing to the first item in the set, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 begin (), rbegin ()，和 rend ().

const_reverse_iterator QSet:: crend () const

返回常量 STL-style reverse iterator pointing to one past the last item in the set, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 end (), rend ()，和 rbegin ().

bool QSet:: empty () const

返回 true if the set is empty. This function is provided for STL compatibility. It is equivalent to isEmpty ().

const_iterator QSet:: end () const

返回常量 STL 样式迭代器 positioned at the imaginary item after the last item in the set.

另请参阅 constEnd () 和 begin ().

iterator QSet:: end ()

这是重载函数。

Returns a non-const STL 样式迭代器 pointing to the imaginary item after the last item in the set.

该函数在 Qt 4.2 引入。

iterator QSet:: erase ( const_iterator pos )

Removes the item at the iterator position pos from the set, and returns an iterator positioned at the next item in the set.

不像 remove (), this function never causes QSet to rehash its internal data structure. This means that it can safely be called while iterating, and won't affect the order of items in the set.

该函数在 Qt 5.7 引入。

另请参阅 remove () 和 find ().

iterator QSet:: erase ( iterator pos )

这是重载函数。

该函数在 Qt 4.2 引入。

const_iterator QSet:: find (const T & value ) const

Returns a const iterator positioned at the item value in the set. If the set contains no item value , the function returns constEnd ().

该函数在 Qt 4.2 引入。

另请参阅 constFind () 和 contains ().

iterator QSet:: find (const T & value )

这是重载函数。

Returns a non-const iterator positioned at the item value in the set. If the set contains no item value , the function returns end ().

该函数在 Qt 4.2 引入。

[static] QSet < T > QSet:: fromList (const QList < T > & list )

返回新的 QSet object containing the data contained in list 。由于 QSet doesn't allow duplicates, the resulting QSet might be smaller than the list ，因为 QList can contain duplicates.

范例：

QStringList list;
list << "Julia" << "Mike" << "Mike" << "Julia" << "Julia";
QSet<QString> set = QSet<QString>::fromList(list);
set.contains("Julia");  // returns true
set.contains("Mike");   // returns true
set.size();             // returns 2
					

另请参阅 toList () 和 QList::toSet ().

iterator QSet:: insert (const T & value )

Inserts item value into the set, if value isn't already in the set, and returns an iterator pointing at the inserted item.

另请参阅 operator<< (), remove ()，和 contains ().

QSet < T > &QSet:: intersect (const QSet < T > & other )

Removes all items from this set that are not contained in the other set. A reference to this set is returned.

另请参阅 intersects (), operator&= (), unite ()，和 subtract ().

bool QSet:: intersects (const QSet < T > & other ) const

返回 true if this set has at least one item in common with other .

该函数在 Qt 5.6 引入。

另请参阅 contains () 和 intersect ().

bool QSet:: isEmpty () const

返回 true 若集不包含元素；否则返回 false。

另请参阅 size ().

reverse_iterator QSet:: rbegin ()

返回 STL-style reverse iterator pointing to the first item in the set, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 begin (), crbegin ()，和 rend ().

const_reverse_iterator QSet:: rbegin () const

这是重载函数。

该函数在 Qt 5.6 引入。

bool QSet:: remove (const T & value )

删除任何出现的项 value from the set. Returns true if an item was actually removed; otherwise returns false .

另请参阅 contains () 和 insert ().

reverse_iterator QSet:: rend ()

返回 STL-style reverse iterator pointing to one past the last item in the set, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 end (), crend ()，和 rbegin ().

const_reverse_iterator QSet:: rend () const

这是重载函数。

该函数在 Qt 5.6 引入。

void QSet:: reserve ( int size )

Ensures that the set's internal hash table consists of at least size buckets.

This function is useful for code that needs to build a huge set and wants to avoid repeated reallocation. For example:

QSet<QString> set;
set.reserve(20000);
for (int i = 0; i < 20000; ++i)
    set.insert(values[i]);
					

Ideally, size should be slightly more than the maximum number of elements expected in the set. size doesn't have to be prime, because QSet will use a prime number internally anyway. If size is an underestimate, the worst that will happen is that the QSet will be a bit slower.

In general, you will rarely ever need to call this function. QSet 's internal hash table automatically shrinks or grows to provide good performance without wasting too much memory.

另请参阅 squeeze () 和 capacity ().

int QSet:: size () const

Returns the number of items in the set.

另请参阅 isEmpty () 和 count ().

void QSet:: squeeze ()

Reduces the size of the set's internal hash table to save memory.

The sole purpose of this function is to provide a means of fine tuning QSet 's memory usage. In general, you will rarely ever need to call this function.

另请参阅 reserve () 和 capacity ().

QSet < T > &QSet:: subtract (const QSet < T > & other )

Removes all items from this set that are contained in the other set. Returns a reference to this set.

另请参阅 operator-= (), unite ()，和 intersect ().

void QSet:: swap ( QSet < T > & other )

Swaps set other with this set. This operation is very fast and never fails.

QList < T > QSet:: toList () const

返回新的 QList containing the elements in the set. The order of the elements in the QList is undefined.

范例：

QSet<QString> set;
set << "red" << "green" << "blue" << ... << "black";
QList<QString> list = set.toList();
qSort(list);
					

另请参阅 fromList () 和 QList::fromSet ().

QSet < T > &QSet:: unite (const QSet < T > & other )

Each item in the other set that isn't already in this set is inserted into this set. A reference to this set is returned.

另请参阅 operator|= (), intersect ()，和 subtract ().

QList < T > QSet:: values () const

返回新的 QList containing the elements in the set. The order of the elements in the QList is undefined.

这如同 toList ().

另请参阅 fromList () 和 QList::fromSet ().

bool QSet:: operator!= (const QSet < T > & other ) const

返回 true 若 other set is not equal to this set; otherwise returns false .

Two sets are considered equal if they contain the same elements.

This function requires the value type to implement operator==() .

另请参阅 operator== ().

QSet < T > QSet:: operator& (const QSet < T > & other ) const

返回新的 QSet that is the intersection of this set and the other set.

另请参阅 intersect (), operator&= (), operator| ()，和 operator- ().

QSet < T > &QSet:: operator&= (const QSet < T > & other )

如同 intersect( other ).

另请参阅 operator& (), operator|= ()，和 operator-= ().

QSet < T > &QSet:: operator&= (const T & value )

这是重载函数。

如同 intersect( other ), if we consider other to be a set that contains the singleton value .

QSet < T > QSet:: operator+ (const QSet < T > & other ) const

返回新的 QSet that is the union of this set and the other set.

另请参阅 unite (), operator|= (), operator& ()，和 operator- ().

QSet < T > &QSet:: operator+= (const QSet < T > & other )

Same as unite( other ).

另请参阅 operator| (), operator&= ()，和 operator-= ().

QSet < T > &QSet:: operator+= (const T & value )

Inserts a new item value and returns a reference to the set. If value already exists in the set, the set is left unchanged.

另请参阅 insert ().

QSet < T > QSet:: operator- (const QSet < T > & other ) const

返回新的 QSet that is the set difference of this set and the other set, i.e., this set - other set.

另请参阅 subtract (), operator-= (), operator| ()，和 operator& ().

QSet < T > &QSet:: operator-= (const QSet < T > & other )

如同 subtract( other ).

另请参阅 operator- (), operator|= ()，和 operator&= ().

QSet < T > &QSet:: operator-= (const T & value )

Removes the occurrence of item value from the set, if it is found, and returns a reference to the set. If the value is not contained the set, nothing is removed.

另请参阅 remove ().

QSet < T > &QSet:: operator<< (const T & value )

Inserts a new item value and returns a reference to the set. If value already exists in the set, the set is left unchanged.

另请参阅 insert ().

bool QSet:: operator== (const QSet < T > & other ) const

返回 true 若 other 集等于此集；否则返回 false .

Two sets are considered equal if they contain the same elements.

This function requires the value type to implement operator==() .

另请参阅 operator!= ().

QSet < T > QSet:: operator| (const QSet < T > & other ) const

返回新的 QSet that is the union of this set and the other set.

另请参阅 unite (), operator|= (), operator& ()，和 operator- ().

QSet < T > &QSet:: operator|= (const QSet < T > & other )

Same as unite( other ).

另请参阅 operator| (), operator&= ()，和 operator-= ().

QSet < T > &QSet:: operator|= (const T & value )

Inserts a new item value and returns a reference to the set. If value already exists in the set, the set is left unchanged.

另请参阅 insert ().

相关非成员

QDataStream & operator<< ( QDataStream & out , const QSet < T > & set )

写入 set 到流 out .

This function requires the value type to implement operator<<() .

另请参阅 QDataStream 运算符格式 .

QDataStream & operator>> ( QDataStream & in , QSet < T > & set )

读取集从流 in into set .

This function requires the value type to implement operator>>() .

另请参阅 QDataStream 运算符格式 .