Why can't I convert this String to a URL?

Question

I have x 2 questions about urls and webViews.

Question 1: I have a string which I am getting from an API that is supposed to be a url. The string is https://godochurch.blob.core.windows.net/sermons/1031/30-1-2017-Vision Sunday-Devotion.mp3

When trying to convert to a url I'm getting nil.

Here is the code:

if let sermonUrl = sermonUrl {

        if let url = URL(string: sermonUrl) {

            let requestObj = URLRequest(url: url)
            webView.loadRequest(requestObj)

        }
    }

I have worked out that the space between 'Vision' and 'Sunday' is the problem.

Should I be encoding the string in some way before trying to convert it to a URL? What's confusing is that if I paste the string into my browser it works just fine, but I notice the browser is percent encoding the space.

If I am supposed to be encoding the string, how do I do that?

Question 2: I see that URL(string: "urlStringHere") is only available from iOS 10. My app needs to work for iOS 9. How can I convert the above code so it works on iOS 9 and 10.

Thanks in advance for your time.

Yes. In fact if I manually percent encode the space for that URL the view opens fine. — thecloud_of_unknowing, Feb 03 '17 at 17:40
@SourLeangChhean i think you are simply restating what I said in my question. I am wondering if there is a standard helper method or something you are supposed to call on a string that might be a url in order to remove spaces. — thecloud_of_unknowing, Feb 03 '17 at 17:47

score 3 · Accepted Answer · edited May 23 '17 at 10:29

3

1: escape that space with %20 or +:

if let url = URL(string: "https://godochurch.blob.core.windows.net/sermons/1031/30-1-2017-Vision%20Sunday-Devotion.mp3") {
    // ...
}

2: URL was introduced with Swift 3, which is compatible with iOS 8 and later. See this question on how to make it work with older versions of iOS.

Edit: the easiest way to percent-escape a URL is to use URLComponents:

var components = URLComponents(string: "https://godochurch.blob.core.windows.net")!
components.path = "/sermons/1031/30-1-2017-Vision Sunday-Devotion.mp3"

if let url = components.url {
    // ... 
}

If you happen to get you URL strings from a webservice and it contains a space, that service is bad. Space is not allowed in an URL. Web browsers relax that rule because they know there are bad URLs out there. Swift won't take it.

edited May 23 '17 at 10:29

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answered Feb 03 '17 at 17:35

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Re 1: Hmm, thats not really answering my question. I know I need to escape the space in the string, but how do I do that? Re. 2: Thanks! – thecloud_of_unknowing Feb 03 '17 at 17:41
@Code Different, ok, that is what I was looking for. Thank you. – thecloud_of_unknowing Feb 03 '17 at 17:59
That's a neat trick. Does that approach automatically use the appropriate allowed character sets for each component of the URL? – Duncan C Feb 03 '17 at 19:34
NSURLComponents/URLComponents is a very useful class. I could have used that 10 years ago on Mac OS. – Duncan C Feb 03 '17 at 19:36
@DuncanC it automatically percent-escapes all components of a URL with the appropriate charsets – Code Different Feb 03 '17 at 19:37
That alone is worth the price of admission. Add the ability to slice and dice URLs into components, and the ability to build URLS **from** components, and it is a real gem. – Duncan C Feb 03 '17 at 19:59

Why can't I convert this String to a URL?

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