NSXMLParser Simple Example

Question

Most of the examples of how to invoke the NSXMLParser are contained within complex projects involving Apps. What does a simple example that demonstrates the callbacks look l

Answer 1

Here is a Swift version of the original Objective-C code below.

It was built and tested using XCode 7.3. In writing the delegate I found it quite handy to copy the function prototypes from the documentation. It is worth noting that Swift is currently a fairly rapidly moving target.

main.swift

import Foundation

// Let's go
print("Main: Started")

// Try to load the file. Display the description of the error if one occurs
var xmlData : NSData
do {
    xmlData = try NSData(contentsOfFile: "/Users/amt/Documents/TestXml/Test.xml",
                         options: .DataReadingMappedIfSafe)
}
catch let error as NSError {
    print("Main: \(error.description)")

    exit(1)
}

// Create a parser and point it at the NSData object containing
// the file we just loaded
var parser : NSXMLParser! = NSXMLParser(data: xmlData)

// Create a parser delegate object and assign it to the parser
// Beware the "weak" reference and don't try to combine the two lines
// of code into one unless you like EXC_BAD_ACCESS exceptions
var parserDelegate : MyXmlParserDelegate = MyXmlParserDelegate()
parser.delegate = parserDelegate

// This example also illustrates some of the namespace functions defined in
// the delegate protocol so enable namespace reporting to see them invoked
parser.shouldReportNamespacePrefixes = true

// Parse the document
if !parser.parse() {
    // If parse() returned false then an error occurred so display is location
    // and details
    let error = parser.parserError
    let line = parser.lineNumber
    let col = parser.columnNumber
    print("Parsing failed at \(line):\(col): \(error?.localizedDescription)")
}

// All done
print("Main: Ended")
exit(0)

MyXmlParserDelegate.swift

import Foundation

class MyXmlParserDelegate:NSObject, NSXMLParserDelegate {

    @objc func parserDidStartDocument(parser: NSXMLParser) {
        print("parserDidStartDocument")
    }

    @objc func parser(parser: NSXMLParser, didStartElement elementName: String,
               namespaceURI: String?, qualifiedName qName: String?,
               attributes attributeDict: [String : String]) {
        print("didStartElement       --> \(elementName)")
    }

    @objc func parser(parser: NSXMLParser, foundCharacters string: String) {
        print("foundCharacters       --> \(string)")
    }

    @objc func parser(parser: NSXMLParser, didEndElement elementName: String,
               namespaceURI: String?, qualifiedName qName: String?) {
        print("didEndElement         --> \(elementName)")
    }

    @objc func parser(parser: NSXMLParser, didStartMappingPrefix prefix: String,
               toURI namespaceURI: String) {
        print("didStartMappingPrefix --> Prefix: \(prefix) toURI: \(namespaceURI)")
    }

    @objc func parser(parser: NSXMLParser, didEndMappingPrefix prefix: String) {
        print("didEndMappingPrefix   --> Prefix: \(prefix)")
    }

    @objc func parserDidEndDocument(parser: NSXMLParser) {
        print("parserDidEndDocument")
    }
}