I need help understanding how to convert NSData into a Int. I first downloaded the textFile from a server by doing this:
let url = NSURL(string: "path to server")!
let data = NSData(contentsOfURL: url)!
print(data) //confirmed there is data
//output in console is <31343231 340a>
When I downloaded the file on my computer, the file looks like this:
I looked around for ways to convert NSData to Int, and came across a technique like this:
var src: Int = 0
data.getBytes(&src, length: sizeof(Int))
print("price: \(src)") //output was 11219279950897
Unfortunately 2929 != 11219279950897. I presume it's something to do with possible white space in the document. Would be grateful if I can get some advice on this!
What about this? (Swift 1.2)
let data = ...
if let
datastring = NSString(data: data, encoding: NSUTF8StringEncoding),
num = (datastring as String).toInt() {
print(num)
}
Hope this helps.
Related
I have a string received from the server and I was trying to decode the string with padding but it is throwing nil as result. I tried codes that are available in stack overflow but of no use. Help will be highly appreciated.
I tried with base64 encoded with ignore unknown characters option and padding, still it throws nil.
let pem = "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"
let decodedData = NSData(base64Encoded: dataStr, options: .ignoreUnknownCharacters)
let length = dataStr.count
dataStr = dataStr.padding(toLength: length + (4 - length % 4) % 4, withPad: "=", startingAt: 0)`
It has to give some decoded data with which I can create a certificate because the response is in the format of .cert.
A certificate is not a string. You cannot create a string from the raw Data.
You can decode the base64 encoded string simply with
let decodedData = Data(base64Encoded: dataStr)
Notes:
Don't use NSData in Swift.
The ignoreUnknownCharacters is not needed.
The padding is wrong. It's only required when encoding the data and the base64 related API of String and Data adds the = characters automatically.
May be It will Help
For Image I am doing like this
I am converting UIImage To data and Converting That data to base64EncodedString
let imageData = UIimage.pngData()
//encode string
let imgBase64Str = imageData?.base64EncodedString(options: .lineLength64Characters) ?? ""
//decoding string to data
let decodedData = Data(base64Encoded: imgBase64Str, options: .ignoreUnknownCharacters)
Here I am encoding my string but it gives an error stated above. What I had done is:
let plainData = (password)?.data(using: String.Encoding(rawValue: String.Encoding.utf8.rawValue))
let base64String = plainData.base64EncodedStringWithOptions(NSData.Base64EncodingOptions.init(rawValue: 0))
It gives me an error on the second line of code.
If anyone can help!
You need to use base64EncodedString() function of NSData.
let base64String = plainData?.base64EncodedString()
This works with Swift 3.0
Actually with update of swift version it gives an error. We can do something like:
let plainData = (password)?.data(using: String.Encoding(rawValue: String.Encoding.utf8.rawValue))
let base64String = plainData?.base64EncodedData(options: NSData.Base64EncodingOptions.init(rawValue: 0))
It solved my problem.
I have an iOS application (written in Swift) that retrieves data from a wcf service in JSON format. One of the data is an image stored as a base64string. However, I was not able to convert the base64string to NSData.
My main purpose is to convert base64string all the way to blob so that I could save that in the database. On the other hand, if you know at least part of it such as from base64string to NSData would be helpful.
Following code would give you the idea of my table
let ItemsDB = Table("Items")
let idDB = Expression<String>("ID")
let nameDB = Expression<String>("Name")
let catDB = Expression<String>("Category")
let uomDB = Expression<String>("UOM")
let priceDB = Expression<Double>("Price")
let imageDB = Expression<Blob>("Image")
let actDB = Expression<Bool>("Active")
To convert from Base64 string to NSData
let nsd: NSData = NSData(base64EncodedString: Image, options: NSDataBase64DecodingOptions.IgnoreUnknownCharacters)!
To Convert to Blob
nsd.datatypeValue
This works:
Swift 3, 4 & 5:
var data = Data(base64Encoded: recording_base64, options: .ignoreUnknownCharacters)
Swift 2:
var data = NSData(base64EncodedString: recording_base64, options: NSDataBase64DecodingOptions.IgnoreUnknownCharacters)
There are lot of example you can find online but most of them are in Objective-c. For example, Converting between NSData and base64 strings
It is pretty straight forward for you to use
NSData(base64EncodedString: String, options: NSDataBase64DecodingOptions)
I'm trying to concatenate two NSData objects into one NSMutableData, and than get them back. For now i'm trying to do it in such way:
Get length of first object.
Write into NSMutableData in such order: first object length, first object, second object.
Code looks like:
let firstString = "first_string";
let secondString = "secondSting";
let firstData = firstString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!
let secondData = secondString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!
let mutableData = NSMutableData()
var length = firstData.length
mutableData.appendBytes(&length, length: sizeof(Int))
mutableData.appendData(firstData)
mutableData.appendData(secondData)
Then I want to get datas back. So I suppose to read first data length and then get two datas.
var length = 0
mutableData.getBytes(&length, length: sizeof(Int))
But when I'm trying to get data I'm getting crash instead:
var data = NSData()
mutableData.getBytes(&data, range: NSMakeRange(sizeof(Int), length))
Maybe somebody know where is my problem or how to get datas?
You can extract the data using subdataWithRange():
let firstData1 = mutableData.subdataWithRange(NSMakeRange(sizeof(Int), length))
if let firstString1 = NSString(data: firstData1, encoding: NSUTF8StringEncoding) as? String {
println(firstString1)
} else {
// bad encoding
}
Your solution
var data = NSData()
mutableData.getBytes(&data, range: NSMakeRange(sizeof(Int), length))
does not work and crashes because NSData is a reference type and
data a pointer to the object. You are overwriting this pointer
and the following bytes in memory.
This works perfectly without a crash in my storyboard. I just omitted the second var before length in order to avoid redefining it.
Here is the output for each line:
"first_string"
"secondSting"
<66697273 745f7374 72696e67> // let firstData = ...
<7365636f 6e645374 696e67> // let secondData = ...
<> // let mutableData = ...
12 // var length = ...
// appending data
<0c000000 00000000>
<0c000000 00000000 66697273 745f7374 72696e67>
<0c000000 00000000 66697273 745f7374 72696e67 7365636f 6e645374 696e67>
0 // length = 0
<0c000000 00000000 66697273 745f7374 72696e67 7365636f 6e645374 696e67>
12 // length
This means you probably have an error somewhere else. You did not redefine length, right?
I keep getting this error :
fatal error: unexpectedly found nil while unwrapping an Optional value
and cannot figure out how to debug it!
Here's my code :
func readCSV() -> Array<String> {
// Creates a new array of strings
var csvArray : Array<String> = Array<String>()
if let url: NSURL = NSURL(string : "URLFROMCSV" ) {
// Creates an Input Stream that will load the datas from our URL
let data :NSData! = NSData(contentsOfURL: url)!
let stream : NSInputStream! = NSInputStream(data: data)
// Opens the receiving stream
stream.open()
// Sets a buffer with a given size size
let bufferSize = 1024
var buffer = Array <UInt8>(count: bufferSize, repeatedValue: 0)
// String variable initialization
var csvFullString : String = ""
// While the stream receives datas, parses datas, convert them into strings and then concatenate them into one big string
while (stream.hasBytesAvailable) {
let readSize = stream.read(&buffer, maxLength: bufferSize)
let csvRaw = NSString (bytes: &buffer, length: readSize, encoding: NSUTF8StringEncoding)
let csvString = csvRaw as String!
csvFullString = csvFullString + csvString
}
// Fills the array with each strings. Separation between strings is made when a Θ character is parsed
csvArray = csvFullString.componentsSeparatedByString("Θ")
// Delete each null string
for(var i = 0 ; i < csvArray.count; i++) {
if(csvArray[i] == "") {
csvArray.removeAtIndex(i)
}
}
}
return csvArray
}
After searching on the web, I'm pretty sure it has something to do with unwrapping elements but the fact is when I debug it, i don't get any nil value anywhere.
PS: Would like to upload a screen but can't because i don't have 10 reputation, so bad!
Thanks in advance!
EDIT : Line let data :NSData! = NSData(contentsOfURL: url)! got the error.
Terry
You're probably creating the error in one of these two lines (though it may show up later):
let data :NSData! = NSData(contentsOfURL: url)!
let stream : NSInputStream! = NSInputStream(data: data)
You're assigning an optional value to an implicitlyUnwrappedOptional type and then using it without checking if you have a valid value.
This is why if let exists. It's a little funny that you've started to indent as if you're using if let but aren't.
Try this instead:
if let url = NSURL(string : "http://gorillaapplications.com/etablissements.csv" ) {
// Creates an Input Stream that will load the datas from our URL
if let data = NSData(contentsOfURL: url) {
let stream = NSInputStream(data: data)
stream.open()
// rest of your code here
}
else {
println("Didn't get a data object")
}
}
else {
println("Didn't get a URL object")
}
You really need to grasp Optionals for Swift. I'd recommend reading my Optionals chapter in this iBook: https://itunes.apple.com/us/book/swift-optionals-generics-for/id943445214?mt=11&uo=4&at=11lMGu
Update:
Since you added a bit more in your comments above, you're saying you get the error on this line: let data: NSData! = NSData(contentsOfURL: url)!. This is because of the ! at the end, which tells Swift you're sure that this function will return a valid value, so just use it, without checking if it's nil first. In your case, the function is returning nil and so your app crashes. Using the sample code I've provided above, you'll see that you'll no longer get a crash, but your code will execute the "Didn't get a data object" line. You'll need to correctly handle the case where you can't load data from that URL.