Feeding the report data from an XML file (Swift)

Report data can come from an XML file.

1. Import the GRE library.

   // You must import the GRE library and add it to the linker options at build time.
   //        -I "$(GREDIR)/lib/swift" -L "$(GREDIR)/lib/swift" -lgre
   import libgre

2. Create a class as the delegate of a Swift XML parser.

   // When implementing the Swift XMLParserDelegate protocol, data are send to a content handler of the GRW C API,
   // by calling the startElement(), attribute(), characters() and endElement() functions.
   private class FileRunner: NSObject, XMLParserDelegate {
       var contentHandler: UnsafeMutablePointer<ContentHandler>
   
       init?(_ contentHandler: UnsafeMutablePointer<ContentHandler>) {
           self.contentHandler = contentHandler
       }
   
       func parser(_ parser: XMLParser, didStartElement elementName: String,
                   namespaceURI: String?, qualifiedName qName: String?,
                   attributes attributeDict: [String : String]) {
           // Send a start element to the content handler.
           startElement(contentHandler, elementName)
           // Send attributes to the content handler.
           for (attributeName, attributeValue) in attributeDict {
               attribute(contentHandler, attributeName, attributeValue)
           }
       }
   
       func parser(_ parser: XMLParser, didEndElement elementName: String,
                   namespaceURI: String?, qualifiedName qName: String?) {
           // Send an end element to the content handler.
           endElement(contentHandler, elementName)
       }
   
       func parser(_ parser: XMLParser, foundCharacters string: String) {
           // Send character data to the content handler.
           characters(contentHandler, string)
       }
   }

3. Create a function that reads and parses the XML file.

   public func runFromXML(_ contentHandler: UnsafeMutablePointer<ContentHandler>, _ fileName: String) {
       // Create an XML parser.
       let fileURL = URL(fileURLWithPath: fileName)
       guard let parser = XMLParser(contentsOf: fileURL) else {
           print("Info: Cannot read data.")
           exit(EXIT_FAILURE)
       }
       // Create the delegate of the XML parser.
       let fileRunner = FileRunner(contentHandler)
       parser.delegate = fileRunner
       // Start the XML parsing.
       parser.parse()
   }

4. Feed the report data from the XML file.

   var designFile: String = "SalesList.4rp"
   var outputFilename: String = "SalesList.pdf
   
   // Create a runtime configuration.
   let runtimeConfiguration = createRuntimeConfiguration(designFile)
   setOutputFileName(runtimeConfiguration, outputFilename)
   selectDevice (runtimeConfiguration, PDF)
   configureDistributedProcessing(runtimeConfiguration, "127.0.0.1", 7000)
   
   // Create a content handler.
   guard let contentHandler = createContentHandler(runtimeConfiguration) else {
       print("Error: Report Writer server may not be started. Launch it with the following command: greportwriter -l 7000")
       exit(EXIT_FAILURE)
   }
   
   // Run report from XML file.
   runFromXML(contentHandler, "my_data_file.xml")
   
   // Destroy the content handler.
   destroy_content_handler (contentHandler)
   
   exit(EXIT_SUCCESS)

<Report>
  <Group>
    <Group>
      <Group>
        <OnEveryRow>
          <orderline.orders.orderid>5</orderline.orders.orderid>
          <orderline.orders.userid>bloggs</orderline.orders.userid>
          <orderline.orders.orderdate>2014-06-24</orderline.orders.orderdate>
          ...
          <lineitemprice>122.0</lineitemprice>
          <overalltotal>122.0</overalltotal>
          <usertotal>122.0</usertotal>
          <ordertotal>122.0</ordertotal>
        </OnEveryRow>
      </Group>
      ...