SwiftSoup is a pure Swift library that allows you to parse, traverse, and manipulate HTML on iOS. It is inspired by the popular Java library Jsoup. To form a valid query using SwiftSoup's selector syntax, you need to understand the CSS selector concept, as SwiftSoup's selector syntax is very similar to CSS selectors.
Here's a quick rundown of the selector syntax in SwiftSoup:
- Selecting by Tag: To select elements by their tag name, you simply use the tag name as the selector.
let paragraphs = try document.select("p")
- Selecting by ID: To select an element by its ID, prefix the ID with
#.
let header = try document.select("#header")
- Selecting by Class: To select elements by their class, prefix the class name with
..
let alerts = try document.select(".alert")
- Attribute Selectors: You can select elements with a specific attribute or attribute value.
- Attribute presence:
[href]selects all elements with anhrefattribute. - Attribute equals:
[type="text"]selects all elements with a type of "text".
- Attribute presence:
let links = try document.select("a[href]")
let textFields = try document.select("input[type=text]")
- Combining Selectors: You can combine selectors to refine your selection.
- Descendant selector:
"div.content p"selects paragraphs within a div with a class of "content". - Child selector:
"ul > li"selects only the immediate list items of ul, not nested list items. - Adjacent sibling selector:
"h1 + p"selects a paragraph directly following an h1.
- Descendant selector:
let contentParagraphs = try document.select("div.content p")
let topLevelListItems = try document.select("ul > li")
let paragraphAfterHeader = try document.select("h1 + p")
- Pseudo-selectors: Pseudo-selectors like
:first-child,:last-child,:nth-child(n), etc., can also be used.
let firstChild = try document.select("div.content p:first-child")
Here's a complete example in Swift using SwiftSoup, demonstrating how to parse an HTML string and select elements using different selectors:
import SwiftSoup
let html = """
<!DOCTYPE html>
<html>
<head>
<title>Sample Page</title>
</head>
<body>
<div id="header">
<h1>Welcome to My Website</h1>
</div>
<div class="content">
<p>This is a paragraph in the content div.</p>
<p class="highlight">This is a highlighted paragraph in the content div.</p>
</div>
<a href="https://example.com">Visit Example.com</a>
<ul>
<li>Item 1</li>
<li>Item 2</li>
<li>Item 3</li>
</ul>
</body>
</html>
"""
do {
let document: Document = try SwiftSoup.parse(html)
// Example selectors
let header = try document.select("#header").first()
let contentDivs = try document.select("div.content")
let highlightedParagraphs = try document.select("p.highlight")
let links = try document.select("a[href]")
let firstListItem = try document.select("ul > li:first-child").first()
// Use the selected elements...
} catch Exception.Error(let type, let message) {
print(message)
} catch {
print("error")
}
When using SwiftSoup, always wrap your code in a do-catch block since the parsing and selecting methods can throw exceptions that need to be handled. The example above demonstrates how to use different types of selectors to extract elements from the parsed HTML document.
