奇怪的Qt代码与字符串 [英] Strange Qt Code with strings
问题描述
我找到了我的朋友的Qt代码,他对两个 QString
使用模运算符,如下所示:
I found my friend's Qt code and he uses the modulo operator on two QString
s like this:
QString result = oneString % twoString;
这是什么意思?
推荐答案
这是另一种(更高效的)连接 QString
的方法,如手册
It's just another (more efficient) way to concatenate QString
s as described in the manual
QStringBuilder使用表达式模板并重新实现'% '
运算符,以便当您使用'%'字符串连接而不是
'+'时,多个子字符串连接将推迟,直到
最终结果即将分配给QString。在这一点上,最终结果所需的
内存量是已知的。然后调用内存
分配器一次以获得所需的空间,并将
子字符串逐个复制到其中。
QStringBuilder uses expression templates and reimplements the '%' operator so that when you use '%' for string concatenation instead of '+', multiple substring concatenations will be postponed until the final result is about to be assigned to a QString. At this point, the amount of memory required for the final result is known. The memory allocator is then called once to get the required space, and the substrings are copied into it one by one.
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