How to access SOAP services from iPhone

Question

I'm planning to develop an app for the iPhone and that app would have to access a couple of SOAP services. While doing some basic checking in the iPhone SDK I was not able to find any support for accessing SOAP services, a bit of Googling lead to the conclusion that there is no support for SOAP in the iPhone SDK.

So if I do want to build that app I'll need to come up with a approach to access SOAP services from the iPhone. What would be the best approach? Any best practices? Did someone already write a library using the functionality that is present in the iPhone SDK to access SOAP services?

(Since the service I need to access is exposed by another party and they only expose it as SOAP, it's unfortunately not an option to switch to another type of interface (e.g. REST based API).

Gero

Answer 1

Here is a swift 4 sample code which execute API calling using SOAP service format.

   func callSOAPWSToGetData() {

        let strSOAPMessage =
            "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                "<soap:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\">" +
                "<soap:Body>" +
                "<CelsiusToFahrenheit xmlns=\"http://www.yourapi.com/webservices/\">" +
                "<Celsius>50</Celsius>" +
                "</CelsiusToFahrenheit>" +
                "</soap:Body>" +
        "</soap:Envelope>"

        guard let url = URL.init(string: "http://www.example.org") else {
            return
        }
        var request = URLRequest.init(url: url)
        let length = (strSOAPMessage as NSString).length
        request.addValue("application/soap+xml; charset=utf-8", forHTTPHeaderField: "Content-Type")
        request.addValue("http://www.yourapi.com/webservices/CelsiusToFahrenheit", forHTTPHeaderField: "SOAPAction")
        request.addValue(String(length), forHTTPHeaderField: "Content-Length")
        request.httpMethod = "POST"
        request.httpBody = strSOAPMessage.data(using: .utf8)

        let config = URLSessionConfiguration.default
        let session = URLSession(configuration: config)
        let task = session.dataTask(with: request) { (data, response, error) in
            guard let responseData = data else {
                print("Error: did not receive data")
                return
            }
            guard error == nil else {
                print("error calling GET on /todos/1")
                print(error ?? "")
                return
            }
            print(responseData)
            let strData = String.init(data: responseData, encoding: .utf8)
            print(strData ?? "")
        }
        task.resume()
    }

Answer 2

My solution was to have a proxy server accept REST, issue the SOAP request, and return result, using PHP.

Time to implement: 15-30 minutes.

Not most elegant, but solid.

Answer 3

You can connect using a tool that I found http://www.wsdl2code.com

SampleServiceProxy *proxy = [[SampleServiceProxy alloc]initWithUrl:@"YOUR
        URL" AndDelegate:self];

[proxy GetDouble];
[proxy GetEnum];
[proxy getEnum:kTestEnumTestEnum2];
[proxy GetInt16];
[proxy GetInt32];
[proxy GetInt64];
[proxy GetString];
[proxy getListStrings];

Answer 4

Have a look at gsoap that includes two iOS examples in the download package under ios_plugin. The tool converts WSDL to code for SOAP and XML REST.

Answer 5

I've historically rolled my own access at a low level (XML generation and parsing) to deal with the occasional need to do SOAP style requests from Objective-C. That said, there's a library available called SOAPClient (soapclient) that is open source (BSD licensed) and available on Google Code (mac-soapclient) that might be of interest.

I won't attest to it's abilities or effectiveness, as I've never used it or had to work with it's API's, but it is available and might provide a quick solution for you depending on your needs.

Apple had, at one time, a very broken utility called WS-MakeStubs. I don't think it's available on the iPhone, but you might also be interested in an open-source library intended to replace that - code generate out Objective-C for interacting with a SOAP client. Again, I haven't used it - but I've marked it down in my notes: wsdl2objc

Answer 6

One word: Don't.

OK obviously that isn't a real answer. But still SOAP should be avoided at all costs. ;-) Is it possible to add a proxy server between the iPhone and the web service? Perhaps something that converts REST into SOAP for you?

You could try CSOAP, a SOAP library that depends on libxml2 (which is included in the iPhone SDK).

I've written my own SOAP framework for OSX. However it is not actively maintained and will require some time to port to the iPhone (you'll need to replace NSXML with TouchXML for a start)