Kanna is a Swift library for parsing HTML and XML, commonly used for web scraping iOS applications. It provides an easy-to-use interface for navigating and manipulating HTML documents.
Character encoding determines how characters are stored in a document. Correctly handling character encoding is crucial when scraping web content because different websites may use different encodings, and misinterpreting the encoding can lead to garbled or incorrect text extraction.
Kanna automatically handles character encodings by using Swift's native string handling, which is Unicode compliant. When you load HTML content into Kanna, it implicitly uses the underlying Swift String initializers, which can automatically detect and correctly interpret the character encoding of the text, provided the HTML document includes the correct charset declaration within the <meta> tag in the <head> section.
Here is an example of how to use Kanna to parse HTML content, assuming the HTML is correctly encoded:
import Kanna
func scrapeHTMLContent(from htmlString: String) {
do {
// Parse the HTML document
let doc = try HTML(html: htmlString, encoding: .utf8)
// Iterate through elements, for example, extracting all 'a' tags
for link in doc.xpath("//a | //A") {
print(link.text ?? "No text content")
print(link["href"] ?? "No href attribute")
}
} catch {
print("Error parsing HTML: \(error)")
}
}
// Example usage with a simple HTML string
let htmlString = """
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Example HTML</title>
</head>
<body>
<a href="https://example.com">An example link</a>
</body>
</html>
"""
scrapeHTMLContent(from: htmlString)
In the above example, the HTML content is assumed to be in UTF-8 encoding, which is the most common encoding for web content. However, if you're dealing with a website that uses a different encoding and you know what that encoding is, you can specify it explicitly when initializing the HTML document:
let doc = try HTML(html: htmlString, encoding: String.Encoding.someOtherEncoding)
Replace someOtherEncoding with the appropriate String.Encoding value that matches the encoding of the HTML document you are scraping.
If the HTML does not have a character encoding specified or if Kanna cannot determine the encoding, you might need to handle the encoding yourself. For instance, you can use external libraries or the native String functionalities to convert the encoding before passing the content to Kanna.
Always ensure that your web scraping activities comply with the terms of service of the website and relevant laws like the GDPR or the Computer Fraud and Abuse Act (CFAA) in the US.
