问题描述
我看到有一个新的正则表达式类 - QRegularExpression 。它只是一个typedef QRegExp，或一个新类，或什么？为什么我们需要它，我们已经有了QRegExp？
I see there is a new class for regular expressions - QRegularExpression. Is it just a typedef for QRegExp, or a new class, or what? And why do we need it, we already have QRegExp?
推荐答案
真的是一个新类，它有改进，但它只在Qt5中可用，所以如果你想在Qt4和Qt5上编译，你不能使用它：
Ok, after some more digging into the docs, I found it really is a new class, it has improvements, but it is only available in Qt5, so you can't use it if you want to compile on both Qt4 and Qt5:
QRegExpression在Qt 5中引入的QRegularExpression类是QRegExp的一个很大的改进，和执行速度。最大的区别是，当请求匹配时，QRegularExpression只保存正则表达式，并且不会修改。相反，返回QRegularExpressionMatch对象，以便检查匹配的结果并提取捕获的子字符串。这同样适用于全局匹配和QRegularExpressionMatchIterator。
The QRegularExpression class introduced in Qt 5 is a big improvement upon QRegExp, in terms of APIs offered, supported pattern syntax and speed of execution. The biggest difference is that QRegularExpression simply holds a regular expression, and it's not modified when a match is requested. Instead, a QRegularExpressionMatch object is returned, in order to check the result of a match and extract the captured substring. The same applies with global matching and QRegularExpressionMatchIterator.
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