setiosflag under the flow of the program

[tarcisio]

I want to change the mode of access to
code
ofstream transfer;
\code

so that I can alternately overwrite or append to it. What kind (type) of variable should I use to hold "ios::app" or "ios::out" ?

This is the point at the program:


code
string label("2");
.....
some code that may chage label to "1";
..........
if (label == "1") {transfer << setiosflags(met hod);};
/code

and I should have method to be either of "ios::app", "ios::out" .

I have tried
code
string method;
/code
and then

code
setiosflags(met hod.c_str())
/code

withouth success. I know that ios::app is equivalent to 8 or is it equivalent to "8"?

Thanks for help
Tarcisio

[weaknessforcats]

setiosflags is a manipulator. You use it with the ofstream insertion operator:

os << setiosflags(std ::ofstream::out | std::ofstream:: app);

Mnaipulators are functions that take an ostream first argument, your own second argument and return and osteam&. This makes them useable with the ostream operator<<.

MyOfstream.open ("Myfile.txt ", std::ofstream:: out | std::ofstream:: app);

The openmode is a bitfield si it's neither 8 nor "8". It's std::ofstream:: app.

Since ofstream derives from ios_base, you can also use ios::out | ios::app.