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diff --git a/xsd-examples/cxx/tree/custom/double/README b/xsd-examples/cxx/tree/custom/double/README new file mode 100644 index 0000000..bf95104 --- /dev/null +++ b/xsd-examples/cxx/tree/custom/double/README @@ -0,0 +1,86 @@ +This example shows how to customize parsing and serialization code for the +xsd:double XML Schema built-in type using the type customization mechanism +provided by the C++/Tree Mapping. For more information on type customization +see the C++/Tree Mapping Customization Guide, particularly sections 1 and 4: + +http://wiki.codesynthesis.com/Tree/Customization_guide + +In this example our schema uses xsd:double to represent a price. There are +two potential problems with this choice of a price type. First, xsd:double +can be serialized in the scientific notation which would be an unusual way +of representing a price. Second, we would like to limit the number of +fraction digits in our prices to 2. Furthermore, we would like to always +have two fraction digits, even if one or both of them are zeros, for +example: 12.99, 12.90, 12.00. + +In case we can modify the schema, a better approach would be to define the +price type as a restriction of the xsd:decimal type (always fixed notation) +and specify the fractionDigits facet to limit the number of fraction digits +to 2. However, there is no way in XML Schema to specify that there should +always be exactly 2 fraction digits. Therefore, it may still be desirable +to customize this price type to get the required serialization behavior. + +Finally, it is worth noting that the behavior achieved in this example via +type customization can also be achieved by compiling your code with the +following macros defined: + +XSD_TREE_DOUBLE_FIXED +XSD_TREE_DOUBLE_PRECISION 2 + +However, the type customization approach while requiring more work is +cleaner since it does not rely on global macro definitions. + +This example consists of the following files: + +order.xsd + XML Schema definition for a simple order vocabulary. + +double-custom.hxx +double-custom.cxx + Custom parsing and serialization code for the xsd:double types. The + double-custom.hxx file is included at the end of the xml-schema.hxx + file described below. + +xml-schema.hxx + C++ types for XML Schema built-in types. + + This header file is generated by the XSD compiler in the + --generate-xml-schema mode using the following command line: + + xsd cxx-tree --generate-xml-schema --generate-serialization \ + --custom-type double=double \ + --hxx-epilogue '#include "double-custom.hxx"' xml-schema.xsd + + The --custom-type option is used to customize the xsd:double type. The + --hxx-epilogue option is used to include the double-custom.hxx file at + the end of this file. + +order.hxx +order.cxx + C++ types are generated by the XSD compiler from order.xsd using the + following command line: + + xsd cxx-tree --generate-serialization --extern-xml-schema xml-schema.xsd \ + order.xsd + + The --extern-xml-schema option is used to include xml-schema.hxx into + order.hxx. + +driver.cxx + Test driver for the example. It creates a sample order and then + writes it to XML to test the custom xsd:double serialization code. + +To compile and link the example manually from the command line we can use +the following commands (replace 'c++' with your C++ compiler name): + +c++ -DXSD_CXX11 -c order.cxx +c++ -DXSD_CXX11 -c double-custom.cxx +c++ -DXSD_CXX11 -c driver.cxx +c++ -o driver driver.o order.o double-custom.o -lxerces-c + +Note that we need to define the XSD_CXX11 preprocessor macro since the +source code includes libxsd headers directly. + +To run the example execute: + +./driver |