How to convert Base64 data and NSData into string

Question

i am new in IOS and i am making a project in which i receive Base64 data from web service. how to convert Base64 data into string and how to open a pdf view in swift and also check that is there any pdf owner application install or not in iPhone .and i want to know that how to convert NSDATA in string swift.Help me example like this is Base64 data JVBERi0xLjQKJcfsj6IKNSAwIG9iago8PC9MZW5ndGggNiAwIFIvRmlsdGVyIC9GbGF0ZURlY29kZT4+CnN0cmVhbQp4nLVcza8ct5GH1rK9ejIU24lkO5GtJ8vWm5E87eY3uXtbYLHAYi8JdItySrABAjhA8v8fUuwmu35kF2fmxbsWDMxjk8VisapYX+TfbudJ6ds5/6s//vj

Like this is nsdata <25504446 2d312e34 0a25c7ec 8fa20a35 2030206f 626a0a3c 3c2f4c65 6e677468 20362030 20522f46 696c7465 72202f46 6c617465 4465636f 64653e3e 0a737472 65616d0a 789cb55c cdaf1cb7 9187d6b2 bd7a3214 db89643b 91ad27cb d69b913c

Answer 1

There are two parts to this question. First, converting the base 64 string into a Data/NSData. But you've done that already, so you don't need help there.

Second, converting that Data/NSData into a string. But, if you look at that file carefully, you'll see that data is a PDF file, not a text string. For example, if I save that as a file and look at it in a hex editor, I can clearly see it's a PDF:

You can't just convert that PDF binary data to a string. (In fact, that's why it was base64-encoded in the first place, because it was complex binary data.)

But you can, for example, use UIDocumentInteractionController to preview the PDF file that you saved to a file.

---

For example:

// convert base 64 string to data

let base64 = "JVBERi0xLjQKJcfsj6IKNSAwIG9iago8PC9MZW5ndGggNiAwIFIvRmlsdGVyIC9GbGF0ZURlY29kZT4+CnN0cmVhbQp4nLVcza8ct5GH1rK9ejIU24lkO5GtJ8vWm5E87eY3uXtbYLHAYi8JdItySrABAjhA8v8fUuwmu35kF2fmxbsWDMxjk8VisapYX+TfbudJ6ds5/6s/"
guard let data = Data(base64Encoded: base64) else {
    print("unable to convert base 64 string to data")
    return
}

// given the data was PDF, let's save it as such

let fileURL = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    .appendingPathComponent("test.pdf")
try! data.write(to: fileURL)

// if it was a string, you could convert the data to string, but this will fail
// because the data is a PDF, not a text string
//
// guard let string = String(data: data, encoding: .utf8) else {
//     print("Unable to convert data into string")
//     return
// }
// print(string)

// So, instead, let's use `UIDocumentInteractionController` to preview the PDF:

let controller = UIDocumentInteractionController(url: fileURL)
controller.delegate = self
controller.presentPreview(animated: true)

Where, the view controller conforms to UIDocumentInteractionControllerDelegate:

extension ViewController: UIDocumentInteractionControllerDelegate {

    func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
        return self

        // or, if this view controller is already in navigation controller, don't 
        // return `self`, like above, but instead return the navigation controller itself
        //
        // return navigationController!
    }

}

Answer 2

From Base64 to Data to String.

let base64String = "dGhpcyBpcyBmb3IgdGVzdGluZw=="
if let data = Data(base64Encoded: base64String) {
    if let string = String(data: data, encoding: .utf8) {
        print(string)
    }
}

From Base64 to NSData to String.

let data = NSData(base64Encoded: base64String, options: .ignoreUnknownCharacters)
    var string = String(data: data, encoding: .utf8)
}