Swift4中用SWXMLHash+Alamofire解析XML报错，求实体映射方案

Hey there! Let's tackle your problem step by step—first fixing that Sequence conformance error, then showing you how to map the XML entries into a struct for cleaner, more maintainable code.

The root issue here is that in SWXMLHash 4.x, the result of xml["feed"]["entry"] is an XMLIndexer type, which doesn't directly conform to the Sequence protocol (so you can't loop over it directly with a for-in). To access the list of entry nodes, you need to use the all property of the XMLIndexer to get a traversable collection.

Here's the corrected request code:

Alamofire.request("https://itunes.apple.com/us/rss/topgrossingapplications/limit=10/xml").response { response in
    debugPrint(response)
    guard let data = response.data else { return }
    let xml = SWXMLHash.parse(data)
    // Access the `all` property to get a sequence of entry nodes
    let entryNodes = xml["feed"]["entry"].all
    for node in entryNodes {
        print(node["title"].text)
    }
}

To make your code more organized, you can map each XML entry tag to a custom struct. SWXMLHash provides the XMLIndexerDeserializable protocol to simplify this process.

Step 1: Define the Struct #

First, create a struct that matches the data you want to extract from the XML. Below is an example that captures common fields from the iTunes RSS feed:

import SWXMLHash

struct AppEntry: XMLIndexerDeserializable {
    let title: String
    let appId: String
    let artistName: String
    let releaseDate: String
    let appUrl: String
    
    static func deserialize(_ node: XMLIndexer) throws -> AppEntry {
        return try AppEntry(
            title: node["title"].value(),
            appId: node["id"]["attributes"]["im:id"].value(),
            artistName: node["im:artist"].value(),
            releaseDate: node["im:releaseDate"]["attributes"]["label"].value(),
            appUrl: node["link"]["attributes"]["href"].value()
        )
    }
}

Step 2: Parse Directly to Struct Array #

Now you can modify your request code to parse all entry nodes directly into an array of AppEntry instances. This uses SWXMLHash's built-in deserialization to handle the mapping automatically:

Alamofire.request("https://itunes.apple.com/us/rss/topgrossingapplications/limit=10/xml").response { response in
    debugPrint(response)
    guard let data = response.data else { return }
    let xml = SWXMLHash.parse(data)
    
    do {
        // Deserialize all entry nodes into an array of AppEntry
        let appEntries: [AppEntry] = try xml["feed"]["entry"].value()
        
        // Use the parsed data
        for app in appEntries {
            print("App: \(app.title) by \(app.artistName) | ID: \(app.appId)")
        }
    } catch {
        print("Parsing error: \(error.localizedDescription)")
    }
}

Notes for Optional Fields #

If some fields in the XML might be missing, you can handle them as optional values in your struct. For example:

struct AppEntry: XMLIndexerDeserializable {
    let title: String
    let appId: String
    let artistName: String? // Optional field
    
    static func deserialize(_ node: XMLIndexer) throws -> AppEntry {
        return AppEntry(
            title: try node["title"].value(),
            appId: try node["id"]["attributes"]["im:id"].value(),
            artistName: node["im:artist"].value() // No `try` here since it's optional
        )
    }
}

内容的提问来源于stack exchange，提问作者Asif Raza