Please don't post external links to images. You only have a few lines of code and an error message that can be posted here.
If you had done that I would be able to copy and paste the code into my answer showing you how to solve the problem. But so you will only get a textual answer.
The error message is quite clear and a small arrow indicates that the passed argument
file02 is the culprit. The following lines tell you that there is a candidate (I have to type it know!):
virtual std::string hashwrapper::getHashFromFile(std::string)
You are passing
file02 which is of type
QFile but the the function
getHashFromFile expects a
std::string.
Assuming that the parameter is a file name, you can use
file01 which is of type
QString after creating a
std::string from that:
QString Z_01 = file_hashing->getHashFromFile(file01.toStdString());
[EDIT]
I missed that the result is assigned to a
QString. So it should be:
QString Z_01 = QString::fromStdString(file_hashing->getHashFromFile(file01.toStdString()));
[/EDIT]
[EDIT2]
Answering a new question raised as solution:
mainwindow.o:-1: In function `__static_initialization_and_destruction_0':
error: undefined reference to `md5wrapper::md5wrapper()'
error: collect2: error: ld returned 1 exit status
You must link with library containing
md5wrapper.
To do this add the library to the the
LIBS configuration in your Qt project file. See also
Adding Libraries to Projects | Qt Creator Manual[
^].
[EDIT]
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