oop - What is indirect object notation, why is it bad, and how does one avoid it?

Question

The title pretty much sums it up, but here's the long version anyway.

After posting a small snippet of perl code, I was told to avoid indirect object notation, "as it has several side effects". The comment referenced this particular line:

my $some_object = new Some::Module(FIELD => 'value');

As this is how I've always done it, in an effort to get with the times I therefore ask:

• What's so bad about it? (specifically)
• What are the potential (presumably negative) side effects?
• How should that line be rewritten?

I was about to ask the commenter, but to me this is worthy of its own post.

Answer 1

The main problem is that it's ambiguous. Does

my $some_object = new Some::Module(FIELD => 'value');

mean to call the new method in the Some::Module package, or does it mean to call the new function in the current package with the result of calling the Module function in the Some package with the given parameters?

i.e, it could be parsed as:

# method call
my $some_object = Some::Module->new(FIELD => 'value');
# or function call
my $some_object = new(Some::Module(FIELD => 'value'));

The alternative is to use the explicit method call notation Some::Module->new(...).

Normally, the parser guesses correctly, but the best practice is to avoid the ambiguity.