Type of argument to keys on reference must be unblessed hashref or arrayref

perl hashref arrayref
Rahul Reddy picture Rahul Reddy · Jun 13, 2013 · Viewed 13.6k times · Source 
    if((scalar keys ($this->{'libraries'}->{$y}->{'cellHash'})) == 0){

This is the line where I am getting the "Type of argument to keys on reference must be unblessed hashref or arrayref" error. Can you help me fix this? I am not posting the code for obvious reasons.

Answer

ikegami picture ikegami · Jun 13, 2013

The new ability of keys to take a reference is broken by design. Perl's development team couldn't figure out how it should work with some references, so it only works for some references. As such, keys's ability to accept a reference is documented to be experimental. Unable to resolve this issue, this "feature" was removed in 5.24. You shouldn't use it since your code will stop working when you upgrade your perl.

You've hit on of those case where keys doesn't work when given a reference. Provide a hash or an array instead. In this case, you probably want

keys(%{ $this->{'libraries'}->{$y}->{'cellHash'} })

The whole thing can be written as follows:

if (!keys(%{ $this->{libraries}{$y}{cellHash} })) { ... }

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