Problems with ' Printf() ' function and format specifiers such as ' %s '

[Mahim2510]

I am doing the unreal course and I am currently at the Bulls and Cows section. So far it’s been great but I am not getting how the Printf() function works and why is it used and also what does the %s and %i format specifiers do. I’d be glad if someone explains all these to me in this context. The picture is attached below.

[DanM]

It’s using one of the printf family of functions from C which does formatted output.

FString::Printf will use printf to create an FString. All of the % specifiers are placeholders and will be replaced by the value of the respective argument

FString::Printf(TEXT("%s %i %f"), TEXT("Hello"), 42, 3.14.f);
                                  ^1-------------2---3^
                             ^ replace with float(3)
                          ^ replace with an int(2)
                      ^ replace with string(1),

Would create an FString with the value "Hello 42 3.14", the placeholders being positional.
The * is needed for HiddenWord as it is an FString and not something printf (function from the C language) knows what to do with; it needs a pointer to a null terminated character array which is what FString::operator*() does.

You can see a table of the format specifiers and what they do here

std::printf, std::fprintf, std::sprintf, std::snprintf - cppreference.com

[Mahim2510]

@DanM

Would create an FString with the value

Thanks for the explanation, I think I get it now.