Does SwiftSoup support CSS pseudo-classes for element selection?

SwiftSoup is a pure Swift library for working with real-world HTML. It provides a very convenient API for extracting and manipulating data, using the best of DOM, CSS, and jquery-like methods. SwiftSoup is a Swift port of the popular Java HTML parser, Jsoup.

However, unlike its Java counterpart, SwiftSoup does not support CSS pseudo-classes for element selection. CSS pseudo-classes, such as :first-child, :last-child, :nth-child(), and :hover, are used in CSS to define special states of elements. In web scraping, pseudo-classes can be particularly useful for selecting elements based on their state or position among siblings.

While Jsoup (Java) has some support for pseudo-class selectors like :first-child, :last-child, and :nth-of-type, SwiftSoup does not implement these selectors. This means that if you need to select elements based on pseudo-classes in Swift, you will have to perform additional steps manually after you've selected a broader set of elements.

Here's how you might select elements using SwiftSoup, and then filter the results based on what would be a pseudo-class in CSS:

import SwiftSoup

let html = """
<ul>
    <li>First</li>
    <li>Second</li>
    <li>Third</li>
</ul>
"""

do {
    let doc: Document = try SwiftSoup.parse(html)
    let lis: Elements = try doc.select("ul > li")

    // Get the first child
    if let firstChild = lis.first() {
        print(try firstChild.text()) // Outputs: First
    }

    // Get the last child
    if let lastChild = lis.last() {
        print(try lastChild.text()) // Outputs: Third
    }

    // Get the nth child (e.g. second child, index starts from 0)
    let index = 1
    if lis.size() > index {
        let nthChild = lis.get(index)
        print(try nthChild.text()) // Outputs: Second
    }

} catch Exception.Error(let type, let message) {
    print(message)
} catch {
    print("error")
}

In the above Swift code, we first parse the HTML and select all list item elements using the select method. Then, we manually retrieve the first and last elements to simulate :first-child and :last-child pseudo-classes, and we access the element at a specific index to simulate :nth-child().

Pseudo-classes that involve interaction states (like :hover, :active, etc.) are not applicable in server-side parsing of static HTML content since they depend on user interactions in a browser environment. If you need to simulate interactions or access dynamically-changed state of an element, you would need to use a browser automation tool like Selenium or a headless browser like Puppeteer for Node.js.