Moose ArrayRef attribute returned as an Array

I have a Moose class with an attribute that is an ArrayRef (read-only) and is manipulated internally by the object. But when someone calls the accessor method I want it to return an Array (or list) not a reference. Not only would this cut down on the amount of dereferencing that the user of the class has to do,开发者_运维知识库 but it will mean they can't accidentally tamper with the same ref that my object is using.

So what's the best way to do this? Some sort of coercion?

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Use Moose::Meta::Attribute::Native::Trait::Array and delegation, e.g.

handles => { my_array => 'elements' }

(via doy on #moose)

auto_deref has the undesirable behavior of still returning a reference if you call the accessor in scalar context.

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While you can use auto-deref, Moose::Manual::BestPractices says that this isn't the best way to do it, and that you should instead consider using Moose::Meta::Attribute::Native to accomplish that functionality.

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Use the auto_deref option:

has my_field => (
    is => 'ro', isa => 'ArrayRef[Str]',
    auto_deref => 1,
    # rest of options...
);

Note that sometimes you won't get an array back when using the reader method, depending on the scalar or list context of the expression. A while ago I ran into a situation where I had to explicitly bring array context to the expression in order to get the dereferencing to work.. I'll add an example if I can find it.