NSData base64Encode返回nil swift

Question

i tryed

let contents = results["contents"] as! String!
let decodedData = NSData(base64EncodedString: contents, 
options:NSDataBase64DecodingOptions())
let decodedString = NSString(data: decodedData!, encoding: NSUTF8StringEncoding)





let contents = results["contents"] as! String!
let decodedData = NSData(base64EncodedString: contents, options:NSDataBase64DecodingOptions.IgnoreUnknownCharacters)
let decodedString = NSString(data: decodedData!, encoding: NSUTF8StringEncoding)



let contents = results["contents"] as! String!
let decodedData = NSData(base64EncodedString: contents, options:NSDataBase64DecodingOptions(rawValue: 0)!)
let decodedString = NSString(data: decodedData!, encoding: NSUTF8StringEncoding)

always EXC_BAC_INSTRUCTION from decodedString maybe decodedData return nil

why NSData return nil

Answer 1

Use .Encoding64CharacterLineLength as option, and apply .base64EncodedStringWithOptions to the data:

if let contents = results["contents"] as? String,
        decodedData = NSData(base64EncodedString: contents, options:NSDataBase64DecodingOptions(rawValue: 0)) {
    let decodedString = decodedData.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)
}

Answer 2

You're using so many force unwrap operators ( ! ); don't do this!

What if results has no mapping for the "contents" key?

What if results has a mapping for the "contents" key but it isn't a String ?

What if results has a mapping for the "contents" key, and it is a String , but it's not valid Base 64 encoded data? In this case, NSData's initialization will fail, and return nil.