NSRangeException in swift

Question

Hello every one i am new in swift, i am facing an issue in my program. i have save some data in 'let defaultStudentId = NSUserDefaults.standardUserDefaults()' but every time the application get stopped. defaultStudentId.objectForKey("studentId") this "studentId" is coming from another ViewController.... i need help here is my code and the error.....

import UIKit

class OTPViewController: ViewController {

    @IBOutlet weak var OTP_code: UITextField!
    let defaultStudentId = NSUserDefaults.standardUserDefaults()
    override func viewDidLoad() {
        super.viewDidLoad()

    }


    @IBAction func confirm(sender: AnyObject) {

        let std_id = defaultStudentId.objectForKey("studentId")
        let sendOTPCode = "StudentId=\(std_id)&CODE=\(self.OTP_code.text)&PartnerID=4B67B239CF3735814C063DB89D750481"
        let url = NSURL(string: "http://serviceforonair.examonair.com/AndroidService.asmx/VerifyOTPAndActivateStudent")
        let request = NSMutableURLRequest(URL: url!)
        request.HTTPMethod = "POST"
        request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
        request.HTTPBody = sendOTPCode.dataUsingEncoding(NSUTF8StringEncoding)
        let task = NSURLSession.sharedSession().dataTaskWithRequest(request){data, response, error in
            if error != nil{
                print(error)
                return
            }
            do{
                let responseString = NSString(data: data!, encoding: NSUTF8StringEncoding)
                var message : String!
                message = responseString?.stringByReplacingCharactersInRange(NSMakeRange(0, 76), withString: "").stringByReplacingOccurrencesOfString("</string>", withString: "")
                print(self.defaultStudentId)

            }
            catch let jsonException{
                print(jsonException)
            }
        }
        task.resume()



    }
}

Error 2016-08-15 20:14:10.555 * First throw call stack: ( 0 CoreFoundation 1 libobjc.A.dylib 2 CoreFoundation 3 CoreFoundation 4 Foundation 5 DBMCI 6 DBMCI 7 CFNetwork 8 CFNetwork 9 Foundation 10 Foundation 11 Foundation 12 Foundation 13 libdispatch.dylib 14 libdispatch.dylib 15 libdispatch.dylib 16 libdispatch.dylib 17 libdispatch.dylib 18 libsystem_pthread.dylib 19 libsystem_pthread.dylib ) libc++abi.dylib: (lldb) DBMCI[21415:143621] * Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFString replaceCharactersInRange:withString:]: Range or index out of bounds' 0x000000010dcedd85 exceptionPreprocess + 165 0x0000000110159deb objc_exception_throw + 48 0x000000010dcedcbd +[NSException raise:format:] + 205 0x000000010dcb90ad mutateError + 221 0x000000010e7c887c -[NSString stringByReplacingCharactersInRange:withString:] + 142 0x000000010d62de96 _TFFC5DBMCI17OTPViewController7confirmFPs9AnyObject_T_U_FTGSqCSo6NSData_GSqCSo13NSURLResponse_GSqCSo7NSError__T_ + 902 0x000000010d622c87 _TTRXFo_oGSqCSo6NSData_oGSqCSo13NSURLResponse_oGSqCSo7NSError__dT__XFdCb_dGSqS__dGSqS0__dGSqS1___dT + 103 0x0000000111118b49 75-[__NSURLSessionLocal taskForClass:request:uploadFile:bodyData:completion:]_block_invoke + 19 0x000000011112b0f2 __49-[__NSCFLocalSessionTask _task_onqueue_didFinish]_block_invoke + 302 0x000000010e82f630 __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK + 7 0x000000010e76a805 -[NSBlockOperation main] + 101 0x000000010e74d725 -[__NSOperationInternal _start:] + 646 0x000000010e74d336 __NSOQSchedule_f + 194 0x000000011197a3eb _dispatch_client_callout + 8 0x000000011196082c _dispatch_queue_drain + 2215 0x000000011195fd4d _dispatch_queue_invoke + 601 0x0000000111962996 _dispatch_root_queue_drain + 1420 0x0000000111962405 _dispatch_worker_thread3 + 111 0x0000000111cb74de _pthread_wqthread + 1129 0x0000000111cb5341 start_wqthread + 13 terminating with uncaught exception of type NSException

vadian vadian · Accepted Answer · 2016-08-15T16:43:35

Basically

let std_id = defaultStudentId.objectForKey("studentId")

returns an optional value, so in a String Interpolation "StudentId=\(std_id)"you will get for example "StudentId=Optional(24)" instead of the expected "StudentId=24" which is certainly not what you want.

Assuming the object for key studentId is a String replace the line above with

guard let std_id = defaultStudentId.stringForKey("studentId") else { return }

It checks if the value for key exists and unwraps the optional value on success otherwise it exits the method.

The error message of the crash is related to the line

message = responseString?.stringByReplacingCharactersInRange(NSMakeRange(0, 76), withString: "").stringByReplacingOccurrencesOfString("</string>", withString: "")

Avoid to hard code the range length, calculate it. If you can't, check the length of the string.

NSRangeException in swift

2 Answers