How can I access the "Content-Type" header of an NSHTTPURLResponse?

Question

Here's my naive first pass code:

var httpUrlResponse: NSHTTPURLResponse? // = (...get from server...)
let contentType = httpUrlResponse?.allHeaderFields["Content-Type"]

I've tried various derivations of this code, but I keep getting compiler warnings/errors related to the basic impedance mismatch between the NSDictionary type of the allHeaderFields property and my desire to just get a String or optional String.

Just not sure how to coerce the types.

Nothingness

Answer 1

You can do something like the following in Swift 3:

if
    let httpResponse = response as? HTTPURLResponse, 
    let contentType = httpResponse.value(forHTTPHeaderField: "Content-Type") 
{
    // use contentType here
}
task.resume()

Obviously, here I'm going from the URLResponse (the response variable) to the HTTPURLResponse. And rather than fetching allHeaderFields, I’m using value(forHTTPHeaderField:) which is typed and uses case-insensitive keys.

Hopefully this illustrates the idea.

For Swift 2, see previous revision of this answer.

Rhiannonrhianon

Why do you need to cast it to NSString before casting it to String? Wouldn't as? String work? – Reprint

That double casting was an early Swift 2 problem, which is now rendered unnecessary. But the use of value(forHTTPHeaderField:), shown in this revised answer, eliminates the String cast that allHeaderFields required, altogether. – Rhiannonrhianon

Answer 2

This works with Xcode 6.1:

let contentType = httpUrlResponse?.allHeaderFields["Content-Type"] as String?

Multiple casts no longer required.

And in Xcode 6.3 with Swift 1.2, this works:

let contentType = httpUrlResponse?.allHeaderFields["Content-Type"] as? String

Nothingness

The second statement works even pre-1.2, but I guess it didn't in September? – Ballard

Answer 3

Could you just use the MIMEType property?

https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSURLResponse_Class/#//apple_ref/occ/instp/NSURLResponse/MIMEType

Maladapted

Answer 4

I use an extension to URLResponse to simplify this one (Swift 3):

extension URLResponse {

    func getHeaderField(key: String) -> String? {
       if let httpResponse = self as? HTTPURLResponse {
           if let field = httpResponse.allHeaderFields[key] as? String {
                return field
            }
        }
        return nil
    }
}

Financial