Can SwiftSoup extract data from HTML5 custom data attributes?

Yes, SwiftSoup, a pure Swift library for working with HTML, can extract data from HTML5 custom data attributes. Custom data attributes in HTML5 are attributes prefixed with data-, allowing you to store extra information on standard, semantic HTML elements without other hacks such as non-standard attributes, extra properties on the DOM, or Node.setUserData().

Here's how you can use SwiftSoup to extract data from custom data attributes:

First, ensure you have SwiftSoup installed in your Swift project. If you're using CocoaPods, you can add it to your Podfile:

pod 'SwiftSoup'

Then run pod install to install the library.

Now, let's say you have an HTML string like this:

<div id="example" data-custom="someValue">Content</div>

You can use SwiftSoup to parse the HTML and extract the value of the custom data attribute as follows:

import SwiftSoup

let html = "<div id=\"example\" data-custom=\"someValue\">Content</div>"

do {
    // Parse the HTML
    let doc: Document = try SwiftSoup.parse(html)

    // Find the element with the ID "example"
    if let element: Element = try doc.getElementById("example") {

        // Extract the value of the "data-custom" attribute
        let customData = try element.attr("data-custom")

        // Print the result
        print("The custom data value is: \(customData)")
    }
} catch Exception.Error(let type, let message) {
    print("An error of type \(type) occurred: \(message)")
} catch {
    print("An unknown error occurred")
}

In the code above:

1. We import the SwiftSoup library.
2. We define a string containing our HTML.
3. We parse the HTML string into a Document object.
4. We find the element with the ID example using getElementById.
5. We extract the value of the data-custom attribute using the attr method.
6. We handle any possible exceptions that might occur during parsing or attribute extraction.

The attr method is used to get the value of an attribute for the first matching element. In this case, it retrieves the value of data-custom, which is someValue.