Swift XMLParser cannot parse the whole string

I tried to parse a let contentString = "<p>abcdefg</p><p>hijklmn</p><p>123456</p>", which are html tags, with XMLParser.
When I print elementName and content between tag in XMLParserDelegate methods, only the first tag(p, abcdefg) was printed.

let contentString = "<p>abcdefg</p><p>hijklmn</p><p>123456</p>"
if let data = contentString.data(using: .utf8) {
    let parser = XMLParser(data: data)
    parser.parse()
}

XMLParserDelegate methods

func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String] = [:]) {
    print(elementName)
}

func parser(_ parser: XMLParser, foundCharacters string: String) {
    print(string)
}

console log
p
abcdefg

I don't know why parser stop parsing at first tag(p)

There are many problems with your code, but the main one here is that your contentString is not valid XML. Because of that, there's no good way to tell the XMLParser to parse the whole string.

(Actually I'm quite impressed with what it did. Instead of choking, it parsed up until the validity of the XML ended, and then stopped.)

Valid XML must consist of a single root element; for example

<root><p>abcdefg</p><p>hijklmn</p><p>123456</p></root>

Once you have modified your XML to be valid, you will need to think about how to deal with the delegate so as to parse that XML. But that's a different matter.