in reply to how to call a sub via variable in library

I've been staring at this unholy construct $self->{&{\&{$testname}}}->($system); for about 15 minutes, And I still haven't a clue what it's meant to do.

Perhaps you could fill in the blanks?

  1. $testname is a string containing the name of a subroutine?
  2. \&{ $testname }; returns a code reference to the named subroutine.
  3. &{ \&{ $testname } } invokes that coderef. Ie, a long winded and obfuscated way of doing: &$testname
  4. $self->{ &{ \&{ $testname } } } Uses the (if any) return code from the subroutine as a key into the object hash.
  5. $self->{ &{ \&{ $testname } } }->( ... ); who's associated value is another coderef, which it invokes ...
  6. $self->{ &{ \&{ $testname } } }->( $system ); passing one variable $system (which is apparently a hashref.)

Unless you have pre-populated the object hash with a key matching every possible return value from every possible test name, and associated an appropriate coderef for all of those keys; that line isn't trying to do what you think it is. (And even if it is, the way it is written is unnecessarily complicated and obfuscate.)

(And a brief glance at the rest of your code makes me think you're writing code you will not be able to maintain.)

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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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Re^2: how to call a sub via variable in library
by Anonymous Monk on Nov 17, 2014 at 19:33 UTC
    I've been staring at this unholy construct $self->{&{\&{$testname}}}->($system); for about 15 minutes, And I still haven't a clue what it's meant to do.
    This is a very obscure and useless feature of Perl. Documented in strict 
    $bar = \&{'foo'};
&$bar;

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    is allowed so that "goto &$AUTOLOAD" would not break under stricture.
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[d/l]

      That bit is obfuscated, but at least understandable.

      It's the invoking of a subroutine from the object hash keyed by the return code of that subroutine that I find completely unlikely.

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
Re^2: how to call a sub via variable in library
by glenn (Scribe) on Nov 17, 2014 at 21:18 UTC
    you have given the best understanding of which i did not even have... Although this is wrong here is what i want to accomplish: $self->&$testname($system). Execute sub '$testname' with '$system' as parameter in object '$self'. Could you help further with this???
[reply]
      here is what i want to accomplish: $self->&$testname($system). Execute sub '$testname' with '$system' as parameter in object '$self'.

      Depends what do you mean by "... in object $self"?

      I see two possible interpretations of that:

      1. You simply want to execute the sub named in $testname (whilst incidentally running inside a method of object $self); in which case all you need is:
        $testname->( $system );

        [download]

        You'll probably need no strict 'refs'; for that.

      2. Alternatively, you might mean that you want to invoke the method of object $self, who's name is held in $testname; in which case all you need is:
        $self->$testname( $system );

        [download]

        Seems to work fine with full strict.

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
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