Error Handle of NSRangeException in swift

Question

I tried it in objective c, with try catch block.It's working fine with this code

    NSString *string = @"This is demo text";
    NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
    //it's(data) length is 17

    @try {
         NSData *subdata = [data subdataWithRange:NSMakeRange(4000, 20)];
    } @catch (NSException *exception) {
        NSLog(@"exception ERROR: %@",exception);
    }

It's print exception error.

But when I tried it with try catch block in swift, it's not giving exception error and app crashed at that point.

 var sourceString = "This is demo text"
        let sourceData = sourceString.data(using: String.Encoding.utf8)!  // sourceData is equivalent to "wav" from question


        guard let subdata = Data(sourceData.subdata(in: 4000 ..< (4000 + 20))) else{
            throw LevelParsingException.InvalidLevelContent
        }

I am trying to handle NSRangeException error in swift 3.

Why are you hardcoding a possibly out-of-range range? Base your range on the actual length of the data. Avoid the possibility of the error. Code defensively. — rmaddy
– rmaddy, Commented Feb 26, 2018 at 5:32
It's a non-catchable programming error to use a bad range in Swift. There's nothing to catch. Write code that only uses a valid range. — rmaddy
– rmaddy, Commented Feb 26, 2018 at 5:39
@rmaddy My answer is same that, how to handle this bacause my data range calculate at run time — Yatendra
– Yatendra, Commented Feb 26, 2018 at 5:41
One cannot catch NSException in Swift, compare stackoverflow.com/a/24023248/1187415 or stackoverflow.com/q/38737880/1187415 — Martin R
– Martin R, Commented Feb 26, 2018 at 5:53

Yatendra · Accepted Answer · 2018-02-28 10:59:04Z

1

At last I reached at following solution that in swift if need to handle range exceptions then we need to do this

var sourceString = "This is demo text"
let sourceData = sourceString.data(using: String.Encoding.utf8)!  // sourceData is equivalent to "wav" from question

Total data length(sourceData.length) should be maximum from your staring point(4000) and length of data(20) which you need to retrieve

guard sourceData.length >= (4000 + 20) else{

   throw LevelParsingException.InvalidLevelContent
}

answered Feb 28, 2018 at 10:59

Yatendra

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