Implicit conversion loses integer precision: 'long long' to 'NSInteger' (aka 'int')

Question

I am trying to assign a variable with type 'long long' to a type NSUInteger, What is the correct way to do that?

my code line:

expectedSize = response.expectedContentLength > 0 ? response.expectedContentLength : 0;

where expectedSize is of type NSUInteger and return type of response.expectedContentLength is of type 'long long'. The variable response is of type NSURLResponse.

The compile error shown is:

Semantic Issue: Implicit conversion loses integer precision: 'long long' to 'NSUInteger' (aka 'unsigned int')

Deceptive

You can do an explicit cast, or did you know this and is your question about more than the "how"? Here's the line with the explicit cast: expectedSize = response.expectedContentLength > 0 ? (NSUInteger)response.expectedContentLength : 0; – Directoire

Answer 1

It's really just a cast, with some range checking:

const long long expectedContentLength = response.expectedContentLength;
NSUInteger expectedSize = 0;

if (NSURLResponseUnknownLength == expectedContentLength) {
    assert(0 && "length not known - do something");
    return errval;
}
else if (expectedContentLength < 0) {
    assert(0 && "too little");
    return errval;
}
else if (expectedContentLength > NSUIntegerMax) {
    assert(0 && "too much");
    return errval;
}

// expectedContentLength can be represented as NSUInteger, so cast it:
expectedSize = (NSUInteger)expectedContentLength;

Triune

< 0 check is not correct. The value -1 means "no expectation that can be arrived at regarding expected content length" (see NSURLResponse.h) – Accoutre

@Dmitry added case to example. it's a very specific implementation detail, which would have been caught. it was meant to demonstrate the process, rather than be a perfect and complete implementation (it still is not). – Triune

Answer 2

you could try the conversion with NSNumber:

  NSUInteger expectedSize = 0;
  if (response.expectedContentLength) {
    expectedSize = [NSNumber numberWithLongLong: response.expectedContentLength].unsignedIntValue;
  }

Reinhardt