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author | Sérgio Martins <sergio.martins@kdab.com> | 2015-06-22 17:21:34 +0100 |
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committer | Sérgio Martins <sergio.martins@kdab.com> | 2015-07-28 19:11:17 +0000 |
commit | 4bced6e7a6928137bb7ac965d2b07223880a3e39 (patch) | |
tree | 4ac4b404574c671286ebae8fdad3e5d0b0b60120 /src/corelib/doc/snippets | |
parent | 07f27fcf6d4f046bbea6c3155efa78128e164da4 (diff) |
Introduce QHash key iterators
So we can have interoperability with algorithms.
Motivated by inefficient code like qDeleteAll(hash.keys())
[ChangeLog][QtCore][QHash] Added key iterators, accessible through
keyBegin() and keyEnd().
Change-Id: I1f9db8a7a4294e1556cbb50b8fe5ebdcf0dc29a2
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Diffstat (limited to 'src/corelib/doc/snippets')
-rw-r--r-- | src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp b/src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp index 43d64fc08e..0ac7cb5769 100644 --- a/src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp +++ b/src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp @@ -298,6 +298,25 @@ while (i != hash.end() && i.key() == "plenty") { } //! [26] +//! [27] +for (QHash<int, QString>::const_iterator it = hash.cbegin(), end = hash.cend(); it != end; ++it) { + cout << "The key: " << it.key() << endl + cout << "The value: " << it.value() << endl; + cout << "Also the value: " << (*it) << endl; +} +//! [27] + +//! [28] +// Inefficient, keys() is expensive +QList<int> keys = hash.keys(); +int numPrimes = std::count_if(keys.cbegin(), keys.cend(), isPrimeNumber); +qDeleteAll(hash2.keys()); + +// Efficient, no memory allocation needed +int numPrimes = std::count_if(hash.keyBegin(), hash.keyEnd(), isPrimeNumber); +qDeleteAll(hash2.keyBegin(), hash2.keyEnd()); +//! [28] + //! [qhashbits] inline uint qHash(const std::vector<int> &key, uint seed = 0) { |