使用Swift提取Nimiq钱包网页中的余额值

Alright, let's tackle this Nimiq wallet balance extraction problem you're facing. Right now you're pulling down the full HTML, but we need to parse that to grab the specific balance value from the <span> element you mentioned. Here's how to do it properly:

First, Understand the Page Structure #

First, you'll need to identify the exact CSS selector for that balance <span>. Open your browser, navigate to the wallet page, right-click the balance element (the one showing "34...") and select Inspect. Once the dev tools open, right-click the <span> element in the DOM and choose Copy > Copy CSS Selector. This gives you a precise selector to target the element.

Option 1: Parse Static HTML with SwiftSoup #

If the page renders the balance directly in the server-sent HTML (not loaded dynamically via JavaScript), you can use a HTML parsing library like SwiftSoup to extract the value cleanly (avoid messy string matching that breaks easily if the page changes).

Step 1: Add SwiftSoup #

Add the SwiftSoup library to your project via Swift Package Manager or CocoaPods:

• For SPM: Add the package dependency in Xcode (search for "SwiftSoup" or use the official repository details)
• For CocoaPods: Add pod 'SwiftSoup' to your Podfile and run pod install

Step 2: Code Implementation #

import SwiftSoup

func fetchNimiqBalance(for address: String) async throws -> String? {
    // Build the full URL
    let urlString = "https://nimiq.watch/#\(address)"
    guard let url = URL(string: urlString) else {
        throw NSError(domain: "WalletError", code: 1, userInfo: [NSLocalizedDescriptionKey: "Invalid wallet address URL"])
    }
    
    // Fetch HTML content (handle errors properly instead of force-unwrapping)
    let htmlContent = try String(contentsOf: url)
    
    // Parse the HTML document
    let doc = try SwiftSoup.parse(htmlContent)
    
    // Replace this selector with the one you copied from your browser
    guard let balanceElement = try doc.select("span.your-balance-class").first() else {
        return nil // Balance element not found
    }
    
    // Extract the text content of the span
    let balanceText = try balanceElement.text()
    return balanceText
}

// Usage example
let targetAddress = "NQ48+8CKH+BA24+2VR3+N249+N8MN+J5XX+74DB+5XJ8"
Task {
    do {
        if let balance = try await fetchNimiqBalance(for: targetAddress) {
            print("Wallet Balance: \(balance)")
        } else {
            print("Could not locate the balance element on the page.")
        }
    } catch {
        print("Error fetching balance: \(error.localizedDescription)")
    }
}

Option 2: Handle Dynamic Content with WKWebView #

If the balance is loaded dynamically via JavaScript (meaning the initial HTML you fetch doesn't contain the balance <span>), you'll need to use WKWebView to fully render the page and execute JavaScript to extract the value.

Code Implementation #

import WebKit

func fetchDynamicNimiqBalance(for address: String, completion: @escaping (Result<String?, Error>) -> Void) {
    let urlString = "https://nimiq.watch/#\(address)"
    guard let url = URL(string: urlString) else {
        completion(.failure(NSError(domain: "WalletError", code: 1, userInfo: [NSLocalizedDescriptionKey: "Invalid wallet address URL"])))
        return
    }
    
    // Initialize WKWebView and set up navigation delegate
    let webView = WKWebView()
    webView.navigationDelegate = BalanceNavigationDelegate(completion: completion)
    webView.load(URLRequest(url: url))
}

// Delegate to handle page load completion
class BalanceNavigationDelegate: NSObject, WKNavigationDelegate {
    private let completion: (Result<String?, Error>) -> Void
    
    init(completion: @escaping (Result<String?, Error>) -> Void) {
        self.completion = completion
        super.init()
    }
    
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        // Execute JavaScript to get the balance text (replace the selector with your copied one)
        webView.evaluateJavaScript("document.querySelector('span.your-balance-class').textContent") { result, error in
            if let error = error {
                self.completion(.failure(error))
                return
            }
            
            // Cast the result to a string and return it
            let balanceText = result as? String
            self.completion(.success(balanceText))
        }
    }
    
    func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
        completion(.failure(error))
    }
}

// Usage example
let targetAddress = "NQ48+8CKH+BA24+2VR3+N249+N8MN+J5XX+74DB+5XJ8"
fetchDynamicNimiqBalance(for: targetAddress) { result in
    switch result {
    case .success(let balance):
        if let balance = balance {
            print("Wallet Balance: \(balance)")
        } else {
            print("Balance element not found after page load.")
        }
    case .failure(let error):
        print("Error: \(error.localizedDescription)")
    }
}

Key Notes #

• Replace the Selector: Make sure to swap out span.your-balance-class with the actual CSS selector you copied from your browser. This is critical—without the right selector, the code won't find the balance.
• Avoid Force Unwrapping: Your original code uses myURL! which can crash if the URL is invalid. Always use guard let or if let to safely handle optional values.
• Error Handling: Both examples include proper error handling to catch network issues, parsing errors, or missing elements.

内容的提问来源于stack exchange，提问作者Lyres