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Qt
Internal/Contributor docs for the Qt SDK. Note: These are NOT official API docs; those are found at https://doc.qt.io/
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Qt
Internal/Contributor docs for the Qt SDK. Note: These are NOT official API docs; those are found at https://doc.qt.io/
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\inmodule QtCore More...
#include <qhash.h>
Collaboration diagram for QHash< Key, T >::iterator:Public Types | |
| typedef std::forward_iterator_tag | iterator_category |
| typedef qptrdiff | difference_type |
| typedef T | value_type |
| typedef T * | pointer |
| typedef T & | reference |
Public Member Functions | |
| constexpr | iterator () noexcept=default |
| Constructs an uninitialized iterator. | |
| const Key & | key () const noexcept |
| Returns the current item's key as a const reference. | |
| T & | value () const noexcept |
| Returns a modifiable reference to the current item's value. | |
| T & | operator* () const noexcept |
| Returns a modifiable reference to the current item's value. | |
| T * | operator-> () const noexcept |
| Returns a pointer to the current item's value. | |
| bool | operator== (const iterator &o) const noexcept |
| bool | operator!= (const iterator &o) const noexcept |
| iterator & | operator++ () noexcept |
The prefix ++ operator ( | |
| iterator | operator++ (int) noexcept |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.The postfix ++ operator ( | |
| bool | operator== (const const_iterator &o) const noexcept |
Returns true if other points to the same item as this iterator; otherwise returns false. | |
| bool | operator!= (const const_iterator &o) const noexcept |
Returns true if other points to a different item than this iterator; otherwise returns false. | |
Friends | |
| class | const_iterator |
| class | QHash< Key, T > |
| class | QSet< Key > |
\inmodule QtCore
The QHash::iterator class provides an STL-style non-const iterator for QHash.
QHash<Key, T>iterator allows you to iterate over a QHash and to modify the value (but not the key) associated with a particular key. If you want to iterate over a const QHash, you should use QHash::const_iterator. It is generally good practice to use QHash::const_iterator on a non-const QHash as well, unless you need to change the QHash through the iterator. Const iterators are slightly faster, and can improve code readability.
The default QHash::iterator constructor creates an uninitialized iterator. You must initialize it using a QHash function like QHash::begin(), QHash::end(), or QHash::find() before you can start iterating. Here's a typical loop that prints all the (key, value) pairs stored in a hash:
Unlike QMap, which orders its items by key, QHash stores its items in an arbitrary order.
Here's an example that increments every value stored in the QHash by 2:
To remove elements from a QHash you can use erase_if(QHash<Key, T> &map, Predicate pred):
Multiple iterators can be used on the same hash. However, be aware that any modification performed directly on the QHash (inserting and removing items) can cause the iterators to become invalid.
Inserting items into the hash or calling methods such as QHash::reserve() or QHash::squeeze() can invalidate all iterators pointing into the hash. Iterators are guaranteed to stay valid only as long as the QHash doesn't have to grow/shrink its internal hash table. Using any iterator after a rehashing operation has occurred will lead to undefined behavior.
If you need to keep iterators over a long period of time, we recommend that you use QMap rather than QHash.
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constexprdefaultnoexcept |
Constructs an uninitialized iterator.
Functions like key(), value(), and operator++() must not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it.
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inlinenoexcept |
Returns the current item's key as a const reference.
There is no direct way of changing an item's key through an iterator, although it can be done by calling QHash::erase() followed by QHash::insert().
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inlinenoexcept |
Returns true if other points to a different item than this iterator; otherwise returns false.
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inlinenoexcept |
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::end() leads to undefined results.
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inlinenoexcept |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.The postfix ++ operator ({i++}) advances the iterator to the next item in the hash and returns an iterator to the previously current item.
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inlinenoexcept |
Returns true if other points to the same item as this iterator; otherwise returns false.
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friend |
1.12.0