Strange Qt Code with strings

Question

I found my friend's Qt code and he uses the modulo operator on two QStrings like this:

QString result = oneString % twoString;

What does it mean?

Answer 1

It's just another (more efficient) way to concatenate QStrings as described in the manual

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.

Answer 2

It is Qt specific way of string construction. Take a look on this page.

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.