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QVarLengthArray 类

template <typename T, qsizetype Prealloc> class QVarLengthArray

QVarLengthArray 类 供低级可变长度数组。 更多...

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

注意： 此类的所有函数 可重入 .

公共类型

  const_iterator
  const_pointer
  const_reference
  const_reverse_iterator
  difference_type
  iterator
  pointer
  reference
  reverse_iterator
  size_type
  value_type

公共函数

  QVarLengthArray (InputIterator first , InputIterator last )
  QVarLengthArray (std::initializer_list<T> args )
  QVarLengthArray (QVarLengthArray<T, Prealloc> && other = Prealloc)
  QVarLengthArray (const QVarLengthArray<T, Prealloc> & other = Prealloc)
  QVarLengthArray (qsizetype size )
  QVarLengthArray ()
QVarLengthArray<T, Prealloc> & operator= (QVarLengthArray<T, Prealloc> && other = Prealloc)
QVarLengthArray<T, Prealloc> & operator= (const QVarLengthArray<T, Prealloc> & other = Prealloc)
  ~QVarLengthArray ()
void append (const T & t )
void append (T && t )
void append (const T * buf , qsizetype size )
const T & at (qsizetype i ) const
T & back ()
const T & back () const
QVarLengthArray::iterator begin ()
QVarLengthArray::const_iterator begin () const
qsizetype capacity () const
QVarLengthArray::const_iterator cbegin () const
QVarLengthArray::const_iterator cend () const
void clear ()
QVarLengthArray::const_iterator constBegin () const
const T * constData () const
QVarLengthArray::const_iterator constEnd () const
bool contains (const AT & value ) const
qsizetype count () const
QVarLengthArray::const_reverse_iterator crbegin () const
QVarLengthArray::const_reverse_iterator crend () const
T * data ()
const T * data () const
bool empty () const
QVarLengthArray::iterator end ()
QVarLengthArray::const_iterator end () const
QVarLengthArray::iterator erase (QVarLengthArray::const_iterator pos )
QVarLengthArray::iterator erase (QVarLengthArray::const_iterator begin , QVarLengthArray::const_iterator end )
T & first ()
const T & first () const
T & front ()
const T & front () const
qsizetype indexOf (const AT & value , qsizetype from = 0) const
void insert (qsizetype i , T && value )
void insert (qsizetype i , const T & value )
void insert (qsizetype i , qsizetype count , const T & value )
QVarLengthArray::iterator insert (QVarLengthArray::const_iterator before , qsizetype count , const T & value )
QVarLengthArray::iterator insert (QVarLengthArray::const_iterator before , T && value )
QVarLengthArray::iterator insert (QVarLengthArray::const_iterator before , const T & value )
bool isEmpty () const
T & last ()
const T & last () const
qsizetype lastIndexOf (const AT & value , qsizetype from = -1) const
qsizetype length () const
void pop_back ()
void prepend (T && value )
void prepend (const T & value )
void push_back (const T & t )
void push_back (T && t )
QVarLengthArray::reverse_iterator rbegin ()
QVarLengthArray::const_reverse_iterator rbegin () const
void remove (qsizetype i )
void remove (qsizetype i , qsizetype count )
qsizetype removeAll (const AT & t )
qsizetype removeIf (Predicate pred )
void removeLast ()
bool removeOne (const AT & t )
QVarLengthArray::reverse_iterator rend ()
QVarLengthArray::const_reverse_iterator rend () const
void replace (qsizetype i , const T & value )
void reserve (qsizetype size )
void resize (qsizetype size )
void shrink_to_fit ()
qsizetype size () const
void squeeze ()
T value (qsizetype i ) const
T value (qsizetype i , const T & defaultValue ) const
QVarLengthArray<T, Prealloc> & operator+= (const T & value )
QVarLengthArray<T, Prealloc> & operator+= (T && value )
QVarLengthArray<T, Prealloc> & operator<< (const T & value )
QVarLengthArray<T, Prealloc> & operator<< (T && value )
QVarLengthArray<T, Prealloc> & operator= (std::initializer_list<T> list )
T & operator[] (qsizetype i )
const T & operator[] (qsizetype i ) const
qsizetype erase (QVarLengthArray<T, Prealloc> & array = Prealloc, const AT & t )
qsizetype erase_if (QVarLengthArray<T, Prealloc> & array = Prealloc, Predicate pred )
size_t qHash (const QVarLengthArray<T, Prealloc> & key = Prealloc, size_t seed = 0)
bool operator!= (const QVarLengthArray<T, Prealloc1> & left = Prealloc1, const QVarLengthArray<T, Prealloc2> & right = Prealloc2)
bool operator< (const QVarLengthArray<T, Prealloc1> & lhs = Prealloc1, const QVarLengthArray<T, Prealloc2> & rhs = Prealloc2)
bool operator<= (const QVarLengthArray<T, Prealloc1> & lhs = Prealloc1, const QVarLengthArray<T, Prealloc2> & rhs = Prealloc2)
bool operator== (const QVarLengthArray<T, Prealloc1> & left = Prealloc1, const QVarLengthArray<T, Prealloc2> & right = Prealloc2)
bool operator> (const QVarLengthArray<T, Prealloc1> & lhs = Prealloc1, const QVarLengthArray<T, Prealloc2> & rhs = Prealloc2)
bool operator>= (const QVarLengthArray<T, Prealloc1> & lhs = Prealloc1, const QVarLengthArray<T, Prealloc2> & rhs = Prealloc2)

详细描述

The C++ language doesn't support variable-length arrays on the stack. For example, the following code won't compile: 

int myfunc(int n)
{
    int table[n + 1];  // WRONG
    ...
    return table[n];
}

The alternative is to allocate the array on the heap (with new ): 

int myfunc(int n)
{
    int *table = new int[n + 1];
    ...
    int ret = table[n];
    delete[] table;
    return ret;
}

However, if myfunc() is called very frequently from the application's inner loop, heap allocation can be a major source of slowdown.

QVarLengthArray is an attempt to work around this gap in the C++ language. It allocates a certain number of elements on the stack, and if you resize the array to a larger size, it automatically uses the heap instead. Stack allocation has the advantage that it is much faster than heap allocation.

范例： 

int myfunc(int n)
{
    QVarLengthArray<int, 1024> array(n + 1);
    ...
    return array[n];
}

In the example above, QVarLengthArray will preallocate 1024 elements on the stack and use them unless n + 1 is greater than 1024. If you omit the second template argument, QVarLengthArray's default of 256 is used.

QVarLengthArry 的值类型必须是 可赋值数据类型 . This covers most data types that are commonly used, but the compiler won't let you, for example, store a QWidget 作为值；取而代之，存储 QWidget *.

QVarLengthArray，像 QList , provides a resizable array data structure. The main differences between the two classes are:

  • QVarLengthArray's API is much more low-level and it lacks some of QList 's functionality.
  • QVarLengthArray doesn't initialize the memory if the value is a basic type. ( QList always does.)
  • QList 使用 隐式共享 as a memory optimization. QVarLengthArray doesn't provide that feature; however, it usually produces slightly better performance due to reduced overhead, especially in tight loops.

In summary, QVarLengthArray is a low-level optimization class that only makes sense in very specific cases. It is used a few places inside Qt and was added to Qt's public API for the convenience of advanced users.

另请参阅 QList .

成员类型文档编制

QVarLengthArray:: const_iterator

Typedef for const T *. Provided for STL compatibility.

QVarLengthArray:: const_pointer

Typedef for const T *. Provided for STL compatibility.

QVarLengthArray:: const_reference

Typedef for const T &. Provided for STL compatibility.

[since 5.6] QVarLengthArray:: const_reverse_iterator

typedef 对于 std::reverse_iterator<const T*> . Provided for STL compatibility.

该 typedef 在 Qt 5.6 引入。

QVarLengthArray:: difference_type

typedef 对于 ptrdiff_t。为兼容 STL 提供。

QVarLengthArray:: iterator

Typedef for T *. Provided for STL compatibility.

QVarLengthArray:: pointer

Typedef for T *. Provided for STL compatibility.

QVarLengthArray:: reference

Typedef for T &. Provided for STL compatibility.

[since 5.6] QVarLengthArray:: reverse_iterator

typedef 对于 std::reverse_iterator<T*> . Provided for STL compatibility.

该 typedef 在 Qt 5.6 引入。

QVarLengthArray:: size_type

typedef 对于 int。为兼容 STL 提供。

QVarLengthArray:: value_type

typedef 对于 T。为兼容 STL 提供。

成员函数文档编制

QVarLengthArray::iterator QVarLengthArray:: insert ( QVarLengthArray::const_iterator before , T && value )

QVarLengthArray::iterator QVarLengthArray:: insert ( QVarLengthArray::const_iterator before , const T & value )

这是重载函数。

插入 value in front of the item pointed to by the iterator before . Returns an iterator pointing at the inserted item.

void QVarLengthArray:: insert ( qsizetype i , T && value )

void QVarLengthArray:: insert ( qsizetype i , const T & value )

插入 value at index position i in the array. If i is 0, the value is prepended to the vector. If i is size (), the value is appended to the vector.

For large arrays, this operation can be slow ( 线性时间 ), because it requires moving all the items at indexes i and above by one position further in memory. If you want a container class that provides a fast insert () function, use std::list instead.

另请参阅 remove ().

void QVarLengthArray:: prepend ( T && value )

void QVarLengthArray:: prepend (const T & value )

插入 value at the beginning of the array.

This is the same as vector.insert(0, value ).

For large arrays, this operation can be slow ( 线性时间 ), because it requires moving all the items in the vector by one position further in memory. If you want a container class that provides a fast prepend () function, use std::list instead.

另请参阅 append () 和 insert ().

[since 5.14] template <typename InputIterator> QVarLengthArray:: QVarLengthArray ( InputIterator first , InputIterator last )

Constructs an array with the contents in the iterator range [ first , last ).

The value type of InputIterator must be convertible to T .

该函数在 Qt 5.14 引入。

[since 5.5] QVarLengthArray:: QVarLengthArray ( std::initializer_list < T > args )

Constructs an array from the std::initializer_list given by args .

This constructor is only enabled if the compiler supports C++11 initializer lists.

该函数在 Qt 5.5 引入。

[since 6.0] QVarLengthArray:: QVarLengthArray ( QVarLengthArray < T , Prealloc > && other = Prealloc)

Move-constructs this variable-length array from other . After the move, other is empty.

该函数在 Qt 6.0 引入。

QVarLengthArray:: QVarLengthArray (const QVarLengthArray < T , Prealloc > & other = Prealloc)

构造副本为 other .

QVarLengthArray:: QVarLengthArray ( qsizetype size )

Constructs an array with an initial size of size 元素。

If the value type is a primitive type (e.g., char, int, float) or a pointer type (e.g., QWidget *), the elements are not initialized. For other types, the elements are initialized with a 默认构造值 .

QVarLengthArray:: QVarLengthArray ()

Constructs an array with an initial size of zero.

[since 6.0] QVarLengthArray < T , Prealloc > &QVarLengthArray:: operator= ( QVarLengthArray < T , Prealloc > && other = Prealloc)

移动赋值 other to this array and returns a reference to this array. After the move, other is empty.

该函数在 Qt 6.0 引入。

QVarLengthArray < T , Prealloc > &QVarLengthArray:: operator= (const QVarLengthArray < T , Prealloc > & other = Prealloc)

赋值 other to this array and returns a reference to this array.

QVarLengthArray:: ~QVarLengthArray ()

Destroys the array.

void QVarLengthArray:: append (const T & t )

Appends item t to the array, extending the array if necessary.

另请参阅 removeLast ().

[since 5.9] void QVarLengthArray:: append ( T && t )

This function overloads append.

注意： Unlike the lvalue overload of append(), passing a reference to an object that is already an element of *this leads to undefined behavior: 

vla.append(std::move(vla[0])); // BUG: passing an object that is already in the container

该函数在 Qt 5.9 引入。

void QVarLengthArray:: append (const T * buf , qsizetype size )

追加 size amount of items referenced by buf 到此数组。

const T &QVarLengthArray:: at ( qsizetype i ) const

Returns a reference to the item at index position i .

i must be a valid index position in the array (i.e., 0 <= i < size ()).

另请参阅 value () 和 operator[] ().

[since 5.0] T &QVarLengthArray:: back ()

如同 last (). Provided for STL-compatibility.

该函数在 Qt 5.0 引入。

[since 5.0] const T &QVarLengthArray:: back () const

这是重载函数。

该函数在 Qt 5.0 引入。

QVarLengthArray::iterator QVarLengthArray:: begin ()

返回 STL 样式迭代器 pointing to the first item in the array.

另请参阅 constBegin () 和 end ().

QVarLengthArray::const_iterator QVarLengthArray:: begin () const

这是重载函数。

qsizetype QVarLengthArray:: capacity () const

Returns the maximum number of elements that can be stored in the array without forcing a reallocation.

The sole purpose of this function is to provide a means of fine tuning QVarLengthArray '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 array, call size ().

另请参阅 reserve () 和 squeeze ().

[since 5.0] QVarLengthArray::const_iterator QVarLengthArray:: cbegin () const

返回常量 STL 样式迭代器 pointing to the first item in the array.

该函数在 Qt 5.0 引入。

另请参阅 begin () 和 cend ().

[since 5.0] QVarLengthArray::const_iterator QVarLengthArray:: cend () const

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

该函数在 Qt 5.0 引入。

另请参阅 cbegin () 和 end ().

void QVarLengthArray:: clear ()

Removes all the elements from the array.

Same as resize(0).

QVarLengthArray::const_iterator QVarLengthArray:: constBegin () const

返回常量 STL 样式迭代器 pointing to the first item in the array.

另请参阅 begin () 和 constEnd ().

const T *QVarLengthArray:: constData () const

Returns a const pointer to the data stored in the array. The pointer can be used to access the items in the array. The pointer remains valid as long as the array isn't reallocated.

This function is mostly useful to pass an array to a function that accepts a plain C++ array.

另请参阅 data () 和 operator[] ().

QVarLengthArray::const_iterator QVarLengthArray:: constEnd () const

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

另请参阅 constBegin () 和 end ().

[since 5.3] template <typename AT> bool QVarLengthArray:: contains (const AT & value ) const

返回 true if the array contains an occurrence of value ；否则返回 false .

This function requires the value type to have an implementation of operator==() .

该函数在 Qt 5.3 引入。

另请参阅 indexOf () 和 lastIndexOf ().

qsizetype QVarLengthArray:: count () const

如同 size ().

另请参阅 isEmpty () 和 resize ().

[since 5.6] QVarLengthArray::const_reverse_iterator QVarLengthArray:: crbegin () const

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

该函数在 Qt 5.6 引入。

另请参阅 begin (), rbegin ()，和 rend ().

[since 5.6] QVarLengthArray::const_reverse_iterator QVarLengthArray:: crend () const

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

该函数在 Qt 5.6 引入。

另请参阅 end (), rend ()，和 rbegin ().

T *QVarLengthArray:: data ()

Returns a pointer to the data stored in the array. The pointer can be used to access and modify the items in the array.

范例： 

QVarLengthArray<int> array(10);
int *data = array.data();
for (int i = 0; i < 10; ++i)
    data[i] = 2 * i;

The pointer remains valid as long as the array isn't reallocated.

This function is mostly useful to pass an array to a function that accepts a plain C++ array.

另请参阅 constData () 和 operator[] ().

const T *QVarLengthArray:: data () const

这是重载函数。

[since 5.0] bool QVarLengthArray:: empty () const

返回 true if the array has size 0; otherwise returns false .

如同 isEmpty (). Provided for STL-compatibility.

该函数在 Qt 5.0 引入。

QVarLengthArray::iterator QVarLengthArray:: end ()

返回 STL 样式迭代器 pointing to the imaginary item after the last item in the array.

另请参阅 begin () 和 constEnd ().

QVarLengthArray::const_iterator QVarLengthArray:: end () const

这是重载函数。

QVarLengthArray::iterator QVarLengthArray:: erase ( QVarLengthArray::const_iterator pos )

Removes the item pointed to by the iterator pos from the vector, and returns an iterator to the next item in the vector (which may be end ()).

另请参阅 insert () 和 remove ().

QVarLengthArray::iterator QVarLengthArray:: erase ( QVarLengthArray::const_iterator begin , QVarLengthArray::const_iterator end )

这是重载函数。

Removes all the items from begin up to (but not including) end . Returns an iterator to the same item that end referred to before the call.

T &QVarLengthArray:: first ()

Returns a reference to the first item in the array. The array must not be empty. If the array can be empty, check isEmpty () before calling this function.

另请参阅 last () 和 isEmpty ().

const T &QVarLengthArray:: first () const

这是重载函数。

[since 5.0] T &QVarLengthArray:: front ()

如同 first (). Provided for STL-compatibility.

该函数在 Qt 5.0 引入。

[since 5.0] const T &QVarLengthArray:: front () const

这是重载函数。

该函数在 Qt 5.0 引入。

[since 5.3] template <typename AT> qsizetype QVarLengthArray:: indexOf (const AT & value , qsizetype from = 0) const

Returns the index position of the first occurrence of value in the array, searching forward from index position from . Returns -1 if no item matched.

This function requires the value type to have an implementation of operator==() .

该函数在 Qt 5.3 引入。

另请参阅 lastIndexOf () 和 contains ().

void QVarLengthArray:: insert ( qsizetype i , qsizetype count , const T & value )

这是重载函数。

插入 count 个副本对于 value at index position i in the vector.

QVarLengthArray::iterator QVarLengthArray:: insert ( QVarLengthArray::const_iterator before , qsizetype count , const T & value )

插入 count 个副本对于 value in front of the item pointed to by the iterator before . Returns an iterator pointing at the first of the inserted items.

bool QVarLengthArray:: isEmpty () const

返回 true if the array has size 0; otherwise returns false .

另请参阅 size () 和 resize ().

T &QVarLengthArray:: last ()

Returns a reference to the last item in the array. The array must not be empty. If the array can be empty, check isEmpty () before calling this function.

另请参阅 first () 和 isEmpty ().

const T &QVarLengthArray:: last () const

这是重载函数。

[since 5.3] template <typename AT> qsizetype QVarLengthArray:: lastIndexOf (const AT & value , qsizetype from = -1) const

Returns the index position of the last occurrence of the value value in the array, searching backward from index position from 。若 from is -1 (the default), the search starts at the last item. Returns -1 if no item matched.

This function requires the value type to have an implementation of operator==() .

该函数在 Qt 5.3 引入。

另请参阅 indexOf () 和 contains ().

[since 5.0] qsizetype QVarLengthArray:: length () const

如同 size ().

该函数在 Qt 5.0 引入。

另请参阅 isEmpty () 和 resize ().

[since 5.0] void QVarLengthArray:: pop_back ()

如同 removeLast (). Provided for STL-compatibility.

该函数在 Qt 5.0 引入。

[since 5.0] void QVarLengthArray:: push_back (const T & t )

Appends item t to the array, extending the array if necessary. Provided for STL-compatibility.

该函数在 Qt 5.0 引入。

[since 5.9] void QVarLengthArray:: push_back ( T && t )

This function overloads push_back.

注意： Unlike the lvalue overload of push_back(), passing a reference to an object that is already an element of *this leads to undefined behavior: 

vla.push_back(std::move(vla[0])); // BUG: passing an object that is already in the container

该函数在 Qt 5.9 引入。

[since 5.6] QVarLengthArray::reverse_iterator QVarLengthArray:: rbegin ()

返回 STL-style reverse iterator pointing to the first item in the variable length array, in reverse order.

该函数在 Qt 5.6 引入。

另请参阅 begin (), crbegin ()，和 rend ().

[since 5.6] QVarLengthArray::const_reverse_iterator QVarLengthArray:: rbegin () const

这是重载函数。

该函数在 Qt 5.6 引入。

void QVarLengthArray:: remove ( qsizetype i )

这是重载函数。

Removes the element at index position i .

另请参阅 insert () 和 replace ().

void QVarLengthArray:: remove ( qsizetype i , qsizetype count )

这是重载函数。

移除 count elements from the middle of the array, starting at index position i .

另请参阅 insert () 和 replace ().

[since 6.1] template <typename AT> qsizetype QVarLengthArray:: removeAll (const AT & t )

Removes all elements that compare equal to t from the array. Returns the number of elements removed, if any.

该函数在 Qt 6.1 引入。

另请参阅 removeOne ().

[since 6.1] template <typename Predicate> qsizetype QVarLengthArray:: removeIf ( Predicate pred )

Removes all elements for which the predicate pred returns true from the array. Returns the number of elements removed, if any.

该函数在 Qt 6.1 引入。

另请参阅 removeAll ().

void QVarLengthArray:: removeLast ()

Decreases the size of the array by one. The allocated size is not changed.

另请参阅 append ().

[since 6.1] template <typename AT> bool QVarLengthArray:: removeOne (const AT & t )

Removes the first element that compares equal to t from the array. Returns whether an element was, in fact, removed.

该函数在 Qt 6.1 引入。

另请参阅 removeAll ().

[since 5.6] QVarLengthArray::reverse_iterator QVarLengthArray:: rend ()

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

该函数在 Qt 5.6 引入。

另请参阅 end (), crend ()，和 rbegin ().

[since 5.6] QVarLengthArray::const_reverse_iterator QVarLengthArray:: rend () const

这是重载函数。

该函数在 Qt 5.6 引入。

void QVarLengthArray:: replace ( qsizetype i , const T & value )

替换项在索引位置 i with value .

i must be a valid index position in the array (i.e., 0 <= i < size ()).

另请参阅 operator[] () 和 remove ().

void QVarLengthArray:: reserve ( qsizetype size )

试图分配内存为至少 size elements. If you know in advance how large the array can get, you can call this function and if you call resize () often, you are likely to get better performance. If size is an underestimate, the worst that will happen is that the QVarLengthArray will be a bit slower.

The sole purpose of this function is to provide a means of fine tuning QVarLengthArray 's memory usage. In general, you will rarely ever need to call this function. If you want to change the size of the array, call resize ().

另请参阅 capacity () 和 squeeze ().

void QVarLengthArray:: resize ( qsizetype size )

Sets the size of the array to size 。若 size is greater than the current size, elements are added to the end. If size is less than the current size, elements are removed from the end.

If the value type is a primitive type (e.g., char, int, float) or a pointer type (e.g., QWidget *), new elements are not initialized. For other types, the elements are initialized with a 默认构造值 .

另请参阅 size () 和 squeeze ().

[since 5.10] void QVarLengthArray:: shrink_to_fit ()

如同 squeeze (). Provided for STL-compatibility.

该函数在 Qt 5.10 引入。

qsizetype QVarLengthArray:: size () const

Returns the number of elements in the array.

另请参阅 isEmpty () 和 resize ().

[since 5.1] void QVarLengthArray:: squeeze ()

Releases any memory not required to store the items. If the container can fit its storage on the stack allocation, it will free the heap allocation and copy the elements back to the stack.

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

该函数在 Qt 5.1 引入。

另请参阅 reserve (), capacity ()，和 resize ().

T QVarLengthArray:: value ( qsizetype i ) const

Returns the value at index position i .

If the index i is out of bounds, the function returns a 默认构造值 . If you are certain that i is within bounds, you can use at () instead, which is slightly faster.

另请参阅 at () 和 operator[] ().

T QVarLengthArray:: value ( qsizetype i , const T & defaultValue ) const

这是重载函数。

If the index i is out of bounds, the function returns defaultValue .

QVarLengthArray < T , Prealloc > &QVarLengthArray:: operator+= (const T & value )

追加 value to the array and returns a reference to this vector.

另请参阅 append () 和 operator<< ().

[since 5.11] QVarLengthArray < T , Prealloc > &QVarLengthArray:: operator+= ( T && value )

这是重载函数。

该函数在 Qt 5.11 引入。

另请参阅 append () 和 operator<< ().

QVarLengthArray < T , Prealloc > &QVarLengthArray:: operator<< (const T & value )

追加 value to the array and returns a reference to this vector.

另请参阅 append () 和 operator+= ().

[since 5.11] QVarLengthArray < T , Prealloc > &QVarLengthArray:: operator<< ( T && value )

这是重载函数。

该函数在 Qt 5.11 引入。

另请参阅 append () 和 operator+= ().

[since 5.5] QVarLengthArray < T , Prealloc > &QVarLengthArray:: operator= ( std::initializer_list < T > list )

Assigns the values of list to this array, and returns a reference to this array.

This constructor is only enabled if the compiler supports C++11 initializer lists.

该函数在 Qt 5.5 引入。

T &QVarLengthArray:: operator[] ( qsizetype i )

Returns a reference to the item at index position i .

i must be a valid index position in the array (i.e., 0 <= i < size ()).

另请参阅 data () 和 at ().

const T &QVarLengthArray:: operator[] ( qsizetype i ) const

这是重载函数。

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[since 6.1] template <typename T, qsizetype Prealloc, typename AT> qsizetype erase ( QVarLengthArray < T , Prealloc > & array = Prealloc, const AT & t )

Removes all elements that compare equal to t from the array array . Returns the number of elements removed, if any.

注意： t is not allowed to be a reference to an element inside array . If you cannot be sure that this is not the case, take a copy of t and call this function with the copy.

该函数在 Qt 6.1 引入。

另请参阅 erase_if ().

[since 6.1] template <typename T, qsizetype Prealloc, typename Predicate> qsizetype erase_if ( QVarLengthArray < T , Prealloc > & array = Prealloc, Predicate pred )

Removes all elements for which the predicate pred returns true from the list array . Returns the number of elements removed, if any.

该函数在 Qt 6.1 引入。

另请参阅 erase ().

[since 5.14] template <typename T, qsizetype Prealloc> size_t qHash (const QVarLengthArray < T , Prealloc > & key = Prealloc, size_t seed = 0)

返回哈希值为 key ，使用 seed 做计算种子。

该函数在 Qt 5.14 引入。

template <typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator!= (const QVarLengthArray < T , Prealloc1 > & left = Prealloc1, const QVarLengthArray < T , Prealloc2 > & right = Prealloc2)

返回 true if the two arrays, specified by left and right , are not equal.

Two arrays are considered equal if they contain the same values in the same order.

This function requires the value type to have an implementation of operator==() .

另请参阅 operator== ().

[since 5.6] template <typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator< (const QVarLengthArray < T , Prealloc1 > & lhs = Prealloc1, const QVarLengthArray < T , Prealloc2 > & rhs = Prealloc2)

返回 true if variable length array lhs is lexicographically less than rhs ；否则返回 false .

This function requires the value type to have an implementation of operator<() .

该函数在 Qt 5.6 引入。

[since 5.6] template <typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator<= (const QVarLengthArray < T , Prealloc1 > & lhs = Prealloc1, const QVarLengthArray < T , Prealloc2 > & rhs = Prealloc2)

返回 true if variable length array lhs is lexicographically less than or equal to rhs ；否则返回 false .

This function requires the value type to have an implementation of operator<() .

该函数在 Qt 5.6 引入。

template <typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator== (const QVarLengthArray < T , Prealloc1 > & left = Prealloc1, const QVarLengthArray < T , Prealloc2 > & right = Prealloc2)

返回 true if the two arrays, specified by left and right , are equal.

Two arrays are considered equal if they contain the same values in the same order.

This function requires the value type to have an implementation of operator==() .

另请参阅 operator!= ().

[since 5.6] template <typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator> (const QVarLengthArray < T , Prealloc1 > & lhs = Prealloc1, const QVarLengthArray < T , Prealloc2 > & rhs = Prealloc2)

返回 true if variable length array lhs is lexicographically greater than rhs ；否则返回 false .

This function requires the value type to have an implementation of operator<() .

该函数在 Qt 5.6 引入。

[since 5.6] template <typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator>= (const QVarLengthArray < T , Prealloc1 > & lhs = Prealloc1, const QVarLengthArray < T , Prealloc2 > & rhs = Prealloc2)

返回 true if variable length array lhs is lexicographically greater than or equal to rhs ；否则返回 false .

This function requires the value type to have an implementation of operator<() .

该函数在 Qt 5.6 引入。