Swift - How to subclass NSMutableURLRequest correctly?

Question

I have subclasses NSMutableURLRequest as follows:

class CustomNSMutableURLRequest: NSMutableURLRequest {

    convenience init(url : URL) {
        self.init(url: url)
        self.httpShouldHandleCookies = false
        self.httpMethod = "GET"
        print("Custom Request!")

    }
}

This causes an infinite loop at the self.init(url: url) line. Using super instead of self doesn't work either. How can I fix this?

Answer 1

Unfortunately, you cannot override the exact convenience initializer within a subclass.

You may need to write something like this:

class CustomNSMutableURLRequest: NSMutableURLRequest {

    convenience init(url : URL) {
        self.init(url: url, cachePolicy: .useProtocolCachePolicy, timeoutInterval: 60)
        self.httpShouldHandleCookies = false
        self.httpMethod = "GET"
        print("Custom Request!")
    }
}

But I'm not sure if subclassing is really needed, I would add some factory method to URLRequest like this:

extension URLRequest {

    public static func customRequest(url: URL) -> URLRequest {
        var result = URLRequest(url: url)
        result.httpShouldHandleCookies = false
        result.httpMethod = "GET"
        print("Custom Request!")
        return result
    }
}

Answer 2

In my experience, you cannot safely subclass NSURLRequest. If you do, you will get fascinating misbehavior with NSURLSession in which responses for one request get incorrectly associated with different requests.

Find a different way, such as using the methods designed for NSURLProtocol to attach arbitrary strings to the request, and attach a string containing a UUID, then use that as a dictionary key. Or use the session identifier in conjunction with the per-task identifier. Either way.