ios - Passing parameters to a JSON web service in Objective C

Question

I'm trying to call a webservice method and pass a parameter to it.

Here is my webservice methods:

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public void GetHelloWorld()
    {
        Context.Response.Write("HelloWorld");
        Context.Response.End();
    }

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public void GetHelloWorldWithParam(string param)
    {
        Context.Response.Write("HelloWorld" + param);
        Context.Response.End();
    }

Here is my objective c code:

NSString *urlString = @"http://localhost:8080/MyWebservice.asmx/GetHelloWorld";
NSURL *url = [NSURL URLWithString:urlString];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod: @"POST"];
[request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];

NSError *errorReturned = nil;
NSURLResponse *theResponse =[[NSURLResponse alloc]init];
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&theResponse error:&errorReturned];
if (errorReturned) 
{
    //...handle the error
}
else 
{
    NSString *retVal = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"%@", retVal);
    //...do something with the returned value        
}

So when I call GetHelloWorld it works great and:

NSLog(@"%@", retVal);

display HelloWorld, but how do I call GetHelloWorldWithParam ? How to pass a parameter ?

I try with:

NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:@"myParameter" forKey:@"param"];    
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dict options:kNilOptions error:&error];

and add the two following lines to the request:

[request setValue:[NSString stringWithFormat:@"%d", [jsonData length]] forHTTPHeaderField:@"Content-Length"];
[request setHTTPBody: jsonData];

I have the error :

System.InvalidOperationException: Missing parameter: test.
   at System.Web.Services.Protocols.ValueCollectionParameterReader.Read(NameValueCollection collection)
   at System.Web.Services.Protocols.HttpServerProtocol.ReadParameters()
   at System.Web.Services.Protocols.WebServiceHandler.CoreProcessRequest()

Thank you for your help! Teddy

Answer 1

I have used your code and modified a bit. Please try following first:

 NSString *urlString = @"http://localhost:8080/MyWebservice.asmx/GetHelloWorldWithParam";
    NSURL *url = [NSURL URLWithString:urlString];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    [request setHTTPMethod: @"POST"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
    NSString *myRequestString = @"param="; // Attention HERE!!!!
    [myRequestString stringByAppendingString:myParamString];
    NSData *requestData = [NSData dataWithBytes:[myRequestString UTF8String] length:[myRequestString length]];
    [request setHTTPBody: requestData];

Rest part is same with your code (starting from the line NSError *errorReturned = nil).

Now normally, this code should work. But if you haven't make the modification below in your web.config, it won't.

Check if your web.config file includes following lines:

<configuration>
    <system.web>
    <webServices>
        <protocols>
            <add name="HttpGet"/>
            <add name="HttpPost"/>
        </protocols>
    </webServices>
    </system.web>
</configuration>

I have solved it this way, hope it works for you too.

If you need more informations, please refer these 2 following questions:
. Add key/value pairs to NSMutableURLRequest
. Request format is unrecognized for URL unexpectedly ending in