如何将打开的文件句柄作为函数的参数传递？

Question

I have a main script that calls a function from another module. I open a file in the main script, and I want to use the filehandle attached to this file as a parameter in the function called (I don't want to open the file in the function because I will be calling the same function on the same file several times, so opening it every time wouldn't make sense).

In my main script:

open(my $IN_FILE, "<input.txt") or die "Can't open: $!\n";
open(my $OUT_FILE, ">output.txt") or die "Can't open: $!\n";

AnotherModule->ProcessDBU($IN_FILE, $OUT_FILE); 

In AnotherModule :

sub ProcessDBU{
    my $IN_FILE = $_[0];
    my $OUT_FILE = $_[1];

    local $/ = ' ';

    while(<$IN_FILE>){
        SomeProcess();
    }
} 

However, when I try to run the script, this error occurs:

readline() on unopened filehandle at AnotherModule.pm line 7.

What's preventing me from using the filehandle? Why is it unopened? What can I do to fix this problem?

Answer 1

You are calling a function as a method.

AnotherModule->ProcessDBU($IN_FILE, $OUT_FILE); 

should be

AnotherModule::ProcessDBU($IN_FILE, $OUT_FILE); 

Three differences:

• Method calls search the inheritance hierarchy,
• method calls ignore prototypes, and
• method calls pass the invocant (what's left of -> ) as the first argument.