The QStringTokenizer class splits strings into tokens along given separators. 更多...
| 頭： | #include <QStringTokenizer> |
| CMake: |
find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(mytarget PRIVATE Qt6::Core) |
| qmake: | QT += core |
| Since: | Qt 6.0 |
| 繼承： | QtPrivate::Tok::HaystackPinning (private), QtPrivate::Tok::NeedlePinning (private), and |
注意： 此類的所有函數 可重入 .
| const_iterator | |
| const_pointer | |
| const_reference | |
| difference_type | |
| iterator | |
| pointer | |
| reference | |
| sentinel | |
| size_type | |
| value_type |
| QStringTokenizer (Haystack haystack , Needle needle , Qt::CaseSensitivity cs , Qt::SplitBehavior sb = Qt::KeepEmptyParts) | |
| QStringTokenizer (Haystack haystack , Needle needle , Qt::SplitBehavior sb = Qt::KeepEmptyParts, Qt::CaseSensitivity cs = Qt::CaseSensitive) | |
| QStringTokenizer::iterator | begin () const |
| QStringTokenizer::iterator | cbegin () const |
| QStringTokenizer::sentinel | cend () const |
| QStringTokenizer::sentinel | end () const |
| LContainer | toContainer (LContainer && c = {}) const & |
| RContainer | toContainer (RContainer && c = {}) const && |
| decltype(QtPrivate::Tok::TokenizerResult<Haystack, Needle>({std::forward<Haystack>(h), std::forward<Needle>(n), flags...})) | qTokenize (Haystack && haystack , Needle && needle , Flags... flags ) |
Splits a string into substrings wherever a given separator occurs, returning a (lazily constructed) list of those strings. If the separator does not match anywhere in the string, produces a single-element list containing this string. If the separator is empty, QStringTokenizer produces an empty string, followed by each of the string's characters, followed by another empty string. The two enumerations Qt::SplitBehavior and Qt::CaseSensitivity further control the output.
QStringTokenizer drives QStringView::tokenize (), but, at least with a recent compiler, you can use it directly, too:
for (auto it : QStringTokenizer{string, separator}) use(*it);
注意：
You should never, ever, name the template arguments of a QStringTokenizer explicitly. If you can use C++17 Class Template Argument Deduction (CTAD), you may write
QStringTokenizer{string, separator}
(without template arguments). If you can't use C++17 CTAD, you must use the
QStringView::split
() or QLatin1StringView::split() member functions and store the return value only in
auto
variables:
auto result = string.split(sep);
This is because the template arguments of QStringTokenizer have a very subtle dependency on the specific string and separator types from with which they are constructed, and they don't usually correspond to the actual types passed.
QStringTokenizer acts as a so-called lazy sequence, that is, each next element is only computed once you ask for it. Lazy sequences have the advantage that they only require O(1) memory. They have the disadvantage that, at least for QStringTokenizer, they only allow forward, not random-access, iteration.
The intended use-case is that you just plug it into a ranged for loop:
for (auto it : QStringTokenizer{string, separator}) use(*it);
or a C++20 ranged algorithm:
std::ranges::for_each(QStringTokenizer{string, separator}, [] (auto token) { use(token); });
The QStringTokenizer iterators cannot be used with classical STL algorithms, because those require iterator/iterator pairs, while QStringTokenizer uses sentinels. That is, it uses a different type, QStringTokenizer::sentinel, to mark the end of the range. This improves performance, because the sentinel is an empty type. Sentinels are supported from C++17 (for ranged for) and C++20 (for algorithms using the new ranges library).
QStringTokenizer is very carefully designed to avoid dangling references. If you construct a tokenizer from a temporary string (an rvalue), that argument is stored internally, so the referenced data isn't deleted before it is tokenized:
auto tok = QStringTokenizer{widget.text(), u','}; // return value of `widget.text()` is destroyed, but content was moved into `tok` for (auto e : tok) use(e);
If you pass named objects (lvalues), then QStringTokenizer does not store a copy. You are responsible to keep the named object's data around for longer than the tokenizer operates on it:
auto text = widget.text(); auto tok = QStringTokenizer{text, u','}; text.clear(); // destroy content of `text` for (auto e : tok) // ERROR: `tok` references deleted data! use(e);
另請參閱 QStringView::split (), QString::split ()，和 QRegularExpression .
[alias]
QStringTokenizer::
const_iterator
此 typedef 提供 STL 樣式 const 迭代器為 QStringTokenizer .
另請參閱 iterator .
[alias]
QStringTokenizer::
const_pointer
彆名化的
value_type *
.
[alias]
QStringTokenizer::
const_reference
彆名化的
value_type &
.
[alias]
QStringTokenizer::
difference_type
Alias for qsizetype.
[alias]
QStringTokenizer::
iterator
此 typedef 提供 STL 樣式 const 迭代器為 QStringTokenizer .
QStringTokenizer does not support mutable iterators, so this is the same as const_iterator.
另請參閱 const_iterator .
[alias]
QStringTokenizer::
pointer
彆名化的
value_type *
.
QStringTokenizer does not support mutable iterators, so this is the same as const_pointer.
[alias]
QStringTokenizer::
reference
彆名化的
value_type &
.
QStringTokenizer does not support mutable references, so this is the same as const_reference.
[alias]
QStringTokenizer::
sentinel
This typedef provides an STL-style sentinel for QStringTokenizer::iterator and QStringTokenizer::const_iterator.
另請參閱 const_iterator .
[alias]
QStringTokenizer::
size_type
Alias for qsizetype.
[alias]
QStringTokenizer::
value_type
彆名化的
const QStringView
or
const QLatin1StringView
, depending on the tokenizer's
Haystack
template argument.
[explicit constexpr]
QStringTokenizer::
QStringTokenizer
(
Haystack
haystack
,
Needle
needle
,
Qt::CaseSensitivity
cs
,
Qt::SplitBehavior
sb
= Qt::KeepEmptyParts)
[explicit constexpr]
QStringTokenizer::
QStringTokenizer
(
Haystack
haystack
,
Needle
needle
,
Qt::SplitBehavior
sb
= Qt::KeepEmptyParts,
Qt::CaseSensitivity
cs
= Qt::CaseSensitive)
Constructs a string tokenizer that splits the string haystack into substrings wherever needle occurs, and allows iteration over those strings as they are found. If needle does not match anywhere in haystack , a single element containing haystack is produced.
cs specifies whether needle should be matched case sensitively or case insensitively.
若 sb is Qt::SkipEmptyParts , empty entries don't appear in the result. By default, empty entries are included.
另請參閱 QStringView::split (), QString::split (), Qt::CaseSensitivity ，和 Qt::SplitBehavior .
返迴常量 STL 樣式迭代器 pointing to the first token in the list.
[constexpr]
QStringTokenizer::sentinel
QStringTokenizer::
cend
() const
如同 end ().
[constexpr]
QStringTokenizer::sentinel
QStringTokenizer::
end
() const
返迴常量 STL-style sentinel pointing to the imaginary token after the last token in the list.
Converts the lazy sequence into a (typically) random-access container of type
LContainer
.
This function is only available if
容器
擁有
value_type
matching this tokenizer's value_type.
If you pass in a named container (an lvalue) for c , then that container is filled, and a reference to it is returned. If you pass in a temporary container (an rvalue, incl. the default argument), then that container is filled, and returned by value.
// assuming tok's value_type is QStringView, then... auto tok = QStringTokenizer{~~~}; // ... rac1 is a QList: auto rac1 = tok.toContainer(); // ... rac2 is std::pmr::vector<QStringView>: auto rac2 = tok.toContainer<std::pmr::vector<QStringView>>(); auto rac3 = QVarLengthArray<QStringView, 12>{}; // appends the token sequence produced by tok to rac3 // and returns a reference to rac3 (which we ignore here): tok.toContainer(rac3);
This gives you maximum flexibility in how you want the sequence to be stored.
這是重載函數。
Converts the lazy sequence into a (typically) random-access container of type
RContainer
.
In addition to the constraints on the lvalue-this overload, this rvalue-this overload is only available when this QStringTokenizer does not store the haystack internally, as this could create a container full of dangling references:
auto tokens = QStringTokenizer{widget.text(), u','}.toContainer(); // ERROR: cannot call toContainer() on rvalue // 'tokens' references the data of the copy of widget.text() // stored inside the QStringTokenizer, which has since been deleted
To fix, store the QStringTokenizer in a temporary:
auto tokenizer = QStringTokenizer{widget.text90, u','}; auto tokens = tokenizer.toContainer(); // OK: the copy of widget.text() stored in 'tokenizer' keeps the data // referenced by 'tokens' alive.
You can force this function into existence by passing a view instead:
func(QStringTokenizer{QStringView{widget.text()}, u','}.toContainer()); // OK: compiler keeps widget.text() around until after func() has executed
If you pass in a named container (an lvalue)for c , then that container is filled, and a reference to it is returned. If you pass in a temporary container (an rvalue, incl. the default argument), then that container is filled, and returned by value.
[constexpr, since 6.0]
template <typename Haystack, typename Needle, typename Flags>
decltype
(
QtPrivate::Tok::TokenizerResult
<
Haystack
,
Needle
>({
std::forward
<
Haystack
>(
h
),
std::forward
<
Needle
>(
n
),
flags
...}))
qTokenize
(
Haystack
&&
haystack
,
Needle
&&
needle
,
Flags
...
flags
)
Factory function for a QStringTokenizer that splits the string haystack into substrings wherever needle occurs, and allows iteration over those strings as they are found. If needle does not match anywhere in haystack , a single element containing haystack is produced.
Pass values from Qt::CaseSensitivity and Qt::SplitBehavior enumerators as flags to modify the behavior of the tokenizer.
You can use this function if your compiler doesn't, yet, support C++17 Class Template Argument Deduction (CTAD). We recommend direct use of QStringTokenizer with CTAD instead.
該函數在 Qt 6.0 引入。