Hello I want to use Paypal in my iphone application, I have find the soapRequest to integrating the paypal API. My code is

NSString *soapMessage =  [NSString stringWithFormat:
@"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" 
"<SOAP-ENV:Envelope xmlns:xsi= \"http://www.w3.org/2001/XMLSchema-instance\" xmlns:SOAP-ENC=\"http://schemas.xmlsoap.org/soap/encoding/\" xmlns:SOAP-ENV=\"http://schemas.xmlsoap.org/soap/envelope/\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" SOAP-ENV:encodingStyle=\"http://schemas.xmlsoap.org/soap/encoding/\">\n"
"<SOAP-ENV:Header>\n" 
"<RequesterCredentials xmlns=\"urn:ebay:api:PayPalAPI\">\n" 
"<Credentials xmlns=\"urn:ebay:apis:eBLBaseComponents\">\n" 
"<Username>api_username</Username>\n" 
"<Password>api_password</Password>\n" 
"<Signature/>\n"     
"<Subject/>\n" 
"</Credentials>\n" 
"</RequesterCredentials>\n" 
"</SOAP-ENV:Header>\n" 
"<SOAP-ENV:Body>\n" 
"<specific_api_name_Req xmlns=\"urn:ebay:api:PayPalAPI\">\n" 
"<specific_api_name_Request>\n" 
"<Version xmlns=urn:ebay:apis:eBLBaseComponents”>service_version</Version>\n" 
"<required_or_optional_fields xsi:type=”some_type_here”>\n"                 
"</required_or_optional_fields>\n" 
"</specific_api_name_Request>\n" 
"</specific_api_name_Req>\n" 
"</SOAP-ENV:Body>\n" 
						  "</SOAP-ENV:Envelope>\n"];

NSLog(@"Soap message===%@",soapMessage);


NSString *parameterString = [NSString stringWithFormat:@"USER=%@&PWD=%@&SIGNATURE=%@&VERSION=57.0&METHOD=SetMobileCheckout&AMT=%.2f&CURRENCYCODE=USD&DESC=%@&RETURNURL=%@", userName, password, signature, donationAmount, @"Some Charge", returnCallURL];

NSLog(parameterString);

NSURL *url = [NSURL URLWithString:paypalUrlNVP];
NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:url];
NSString *msgLength = [NSString stringWithFormat:@"%d", [parameterString length]];

[theRequest addValue: msgLength forHTTPHeaderField:@"Content-Length"];
[theRequest setHTTPMethod:@"POST"];
[theRequest setHTTPBody: [parameterString dataUsingEncoding:NSUTF8StringEncoding]];


NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

if( theConnection ){
    webData = [[NSMutableData data] retain];
//	[self displayConnectingView];

}else{
    NSLog(@"theConnection is NULL");
}

But here I am not getting the value of paypalUrlNVP. How can i get it?? And if possible then please give some example of paypalAPI integration in iphone.

I also want to use checkout functionality.I am new in this field so I have no idea about it. So, kindly give me whole sample code. Thanks in advance.