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From "Ned Rockson" <nrock...@stanford.edu>
Subject Re: Problem with autogenerated C++ Records using bin/rcc
Date Thu, 17 Jan 2008 20:21:23 GMT
Okay, that makes sense.  It seems strange to return a reference to a
string object that's not const.  Doesn't this break some C++ coding
standards?  It seems it should return a pointer or have a set method
to maintain symmetry between the two languages.  The counter argument,
of course, is that it's easier to not have a set method and return
some form of reference (be it reference or pointer).

Thanks for the response!


On Jan 10, 2008 8:25 PM, Vivek Ratan <vivekr@yahoo-inc.com> wrote:
> Hi Ned.
> The generated C++ class does not have an explicit constructor, as you've
> pointed out. This is by design. the fields in the DDL class definition
> become private members of the C++ class. It is expected that you assign
> values to each one of them separately, rather than through a constructor.
> There are explicit setters for basic types such as bools or ints. However,
> for strings, you get a reference to the private string member variable
> (using a getter) and then set it. So, in your example, you could do
> something like this:
> Text t = new Text();
> t.getText().assign("whatever value you want"); // assign a value to the
> 'text' field
> Suppose your class Text had an additional bool parameter:
> module io {
> class Text {
>     ustring text;
>     boolean b;
> }
> }
> There'd be a setter for 'b' in the generated C++ class, and you'd do
> something like:
> Text t = new Text();
> t.setB(true);
> It's only for the more complex types (strings, maps, vectors) that you don't
> have explicit setters. You use a getter to get a reference object to the
> member variable, then assign values to it.
> AFAIK, the C++ generated classes are not broken. They're a bit different
> from the Java classes, which have setters for each field (and you could
> discus whether the C++ and Java classes should look more like each other),
> but they work.
> -----Original Message-----
> From: nedrocks@gmail.com [mailto:nedrocks@gmail.com] On Behalf Of Ned
> Rockson
> Sent: Thursday, January 10, 2008 1:34 AM
> To: hadoop-user@lucene.apache.org
> Subject: Problem with autogenerated C++ Records using bin/rcc
> Recently I've been trying to autogenerate some data structures that will
> work for both C++ and Java.  I've made many that work with Java, but every
> time I try to generate one for C++ the generator breaks down.  For instance,
> I was trying to create a Text class for C++, so I created a text.jr:
> module io {
> class Text {
>     ustring text;
> }
> }
> that in Java works fine, but in C++, this is generated (implementation is
> fine for the methods defined):
> #ifndef __TEXT_DDL__
> #define __TEXT_DDL__
> #include "recordio.hh"
> namespace io {
>   class Text : public ::hadoop::Record {
>     private:
>      ::std::string text;
>     public:
>     virtual void serialize(::hadoop::OArchive& a_, const char* tag) const;
>     virtual void deserialize(::hadoop::IArchive& a_, const char* tag);
>     virtual const ::std::string& type() const;
>     virtual const ::std::string& signature() const;
>     virtual bool operator<(const Text& peer_) const;
>     virtual bool operator==(const Text& peer_) const;
>     virtual ~Text() {};
>     virtual const  ::std::string& getText() const {
>       return text;
>     }
>     virtual  ::std::string& getText() {
>       return text;
>     }
>   }; // end record Text
> } // end namespace io
> #endif //TEXT_DDL__
> What is obviously missing is
> -a constructor,
> -a setter (there are getters for const and non-const...)
> This is with hadoop-0.15.1 and I've also tried following the examples given
> in the API to no luck.  Thanks for any feedback!

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