Use covariant return type for clone()
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Key: AMQCPP-34
URL: https://issues.apache.org/activemq/browse/AMQCPP-34
Project: ActiveMQ C++ Client
Issue Type: Improvement
Components: CMS Impl
Affects Versions: 1.1
Reporter: Albert Strasheim
Assigned To: Nathan Mittler
Attachments: covariant-clones.diff
The cms::Message type has a pure virtual clone() method that returns a
cms::Message*. cms::BytesMessage doesn't have a clone method. So it continues
down the inheritance chain until we get to classes like
activemq::connector::stomp::commands::TextMessageCommand which implement
clone() and define it to return cms::Message*.
This means that in my message listener I have to cast the result of a
BytesMessage->clone() (which I already know is a BytesMessage) to BytesMessage
before I can use it as such.
Instead, BytesMessage should override clone() with another pure virtual that
returns cms::BytesMessage. I think this is called a covariant return type.
After that, TextMessageCommand's clone should probably be modified to return
TextMessageCommand*. I don't know if there's anything in between that warrants
a clone with a covariant return type.
Fixing this will make the library slightly easier to use.
Basic patch attached. There's probably more places to fix. Patch also has a few
typo fixes.
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