Re^4: $dbh could not be passed to function unless another variable is also passed

[tukusejssirs]

Probably I still miss something.

I have another function called create_table and the db handle does not pass correctly (should I bless it?). I does work when I create the handle within the function.

create_table($dbh, $table, "record_date char(20)");

sub create_table {
    use DBI;

    # Variables
    my $sth;
        # Database handle
        my $dbh = "$_[0]";

        # Table name and optionally schema name (schema.table)
        my $table = "$_[1]";

        # Columns and their type
        my $cols_type = "$_[2]";
    # } else {
    #     die RED, "ERROR: You have to supply database handle, table n
+ame, the columns list with their type and if you to disconnect the da
+tabase connection.\n       Stopped$!";
    # }

    # Create table
    $sth = $dbh->prepare("create table $table ($cols_type);");
    $sth->execute();
    print "INFO: The table has been created successfully.\n";

    return;
}

[Corion]

my $dbh = "$_[0]";

What is in $dbh and why do you force it to a string?

Also, what is the error message? It is most likely something like Can't call method prepare on DBD::foo::dbh, but telling us the exact error message helps us much better diagnose your situation.

The solution is to not quote variables when you don't need it. Remove the double quotes:

my $dbh = $_[0];

[tukusejssirs]

Corion: The error was Can't locate object method "prepare" via package "DBI::db=HASH(0x215bc78)" (perhaps you forgot to load "DBI::db=HASH(0x215bc78)"?)

Fletch and Corion:

You are right. When I removed the quotes (leaving only my $dbh = $_[0];), it works as expected.

Anyway, what exactly does ‘The solution is to not quote variables when you don't need it.’ mean? That I should quote only strings?

Thank you both!

[hippo]

I should quote only strings?

Yes

[dsheroh]

Anyway, what exactly does ‘The solution is to not quote variables when you don't need it.’ mean? That I should quote only strings?

When you put quotes around something, you turn that thing into a string. You can quote whatever you want to, but, after you quote it, it will be a string, so you should only quote things that you want to be strings.

But you should also remember what already is a string and avoid re-quoting existing strings, partly because it's wasted keystrokes, partly because it's potentially inefficient (it's less work to just use the existing string than to change the existing string into a new string and then use the new one), and partly because there could be some edge cases where quoting the existing string might change it or otherwise break something.

[Fletch]

You've stringified all three of your arguments which isn't what you want to do. A DBI handle is an object which is (usually) implemented as a reference to a data structure such as a hash. When you pass it through double quotes you're breaking that reference (hand waving a bit here; see perlobj for more details) so when you try and call methods upon it you're trying to call methods on a string value (hence your error).