I've written these two function
func locallySave(_ data: Data?, for utility: Utility) throws {
var fileURL = try FileManager.default.url(for: .applicationSupportDirectory,
in: .userDomainMask,
appropriateFor: nil,
create: true)
fileURL.appendPathComponent(Constants.appShortName)
fileURL.appendPathComponent("\(utility).json")
do {
try data?.write(to: fileURL)
} catch {
print("Error: \(error)")
throw error
}
}
and
func locallyLoad(_ utility: Utility) throws -> Data? {
var fileURL = try FileManager.default.url(for: .applicationSupportDirectory,
in: .userDomainMask,
appropriateFor: nil,
create: false)
fileURL.appendPathComponent(Constants.appShortName)
fileURL.appendPathComponent("\(utility).json")
do {
let data = try Data(contentsOf: fileURL)
return data
} catch {
print("Error: \(error)")
throw error
}
}
I think I've got one of two potential bugs in these function.
The first is that I've set create: true in the save function which should make it so if there isn't any file/directory, it will create them.
The second is that it might be creating them, but whenever I run the app, the directory (in the simulator) seems to be changing so I don't know if it's ever going to pull the file if it is there.
For example if I run the app, it will say the URL is something like
/Users/<MyUsername>/Library/Developer/CoreSimulator/Devices/C78E5655-0A29-4FA6-9EC3-20317881C18F/data/Containers/Data/Application/17F82456-9C7A-4D67-988E-88843B3446D8/Library/Application Support/AppTemplate/<SomeUtility>.json
but if I run the app again, I'll get something like
/Users/<MyUsername>/Library/Developer/CoreSimulator/Devices/C78E5655-0A29-4FA6-9EC3-20317881C18F/data/Containers/Data/Application/0397D6F1-94EC-4EF2-9F3C-68764109F845/Library/Application Support/AppTemplate/<SomeUtility>.json
Notice how the second string of digits is completely different.
I don't think it's all the second error because where I go to the fileURL in finder, there's nothing there and it doesn't look like anything has been created at all.
The fileURL in both functions always comes out to be the same for both functions in the debugger. How do I get FileManager to create the file if it doesn't exist and how do I make sure it's always pulling from the same directory it will have saved to?
The error I get is NSUnderlyingError=0x600000fb0480 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}}
Thanks
Related
There's an online site here called Repl.it that gives you an in-browser REPL environment for a ton of languages. It's great to prove out code that you post here on SO. (I think you can even include it here actually but I wasn't successful in embedding mine.)
Anyway, when using Swift, I'm wondering if it's possible to perform file read/write persistence up there. I haven't found any articles that say yes, but I have found some that show them talking about how much storage you have, and it is supposed to be the full Swift runtime with all features, so I'm not sure.
This code fails however, saying it can't be performed.
import Foundation
let file = "file.txt" //this is the file. we will write to and read from it
let text = "some text" //just a text
if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
let fileURL = dir.appendingPathComponent(file)
//writing
do {
try text.write(to: fileURL, atomically: false, encoding: .utf8)
}
catch {
print(error)
}
//reading
do {
let text2 = try String(contentsOf: fileURL, encoding: .utf8)
print("Read back in '\(text2)'")
}
catch {/* error handling here */}
}
else{
print("Couldn't get document directory")
}
You can open it here... Swift File Persistence REPL
I admit I'm 90% sure this isn't the right place for this, but since Repl.it does let you play with and execute Swift and this is a question about what Swift is needed to accomplish this, I figured I'd try!
I am working on an app where I am trying to write data to a file. Basically the user can set the save directory and then I want to be able to check to see if the file exists. If it doesn't then create it and write the data. If it does exist I want to update/append a string to the end of the file. I have tried following many examples and guides online and it seems everyone is doing this differently. I apologize ahead of time if I am missing something super simple or if this has been asked a hundred times.
I have mostly been working off of this example with no success
Append text or data to text file in Swift
#IBAction func addVariance(_ sender: Any) {
let csvString = "08-06-2019,10:00 AM,10:23 AM,23,Offline,Test"
let directoryURL = URL(string: "/Users/username/Desktop/CSVtest")
let fileURL = directoryURL!.appendingPathComponent("/variances.csv")
let data = NSData(data: csvString.data(using: String.Encoding.utf8, allowLossyConversion: false)!)
if FileManager.default.fileExists(atPath: fileURL.path) {
var err:NSError?
if let fileHandle = try? FileHandle(forUpdating: fileURL) {
fileHandle.seekToEndOfFile()
fileHandle.write(data as Data)
fileHandle.closeFile()
}
else {
print("Can't open fileHandle \(String(describing: err))")
}
}
else {
var err:NSError?
do {
try data.write(to: URL(fileURLWithPath: fileURL.path), options: .atomic)
} catch {
print(error)
}
}
}
When trying to run this function when there is a file in the folder named "variances.csv" I get "Can't open fileHandle nil".
I have tried break points and print() lines. It doesn't seem to be getting past "if let fileHandle = try? FileHandle(forUpdating: fileURL)" and I can't figure out why. fileURL is not nil.
When I try running this function outputting to an empty directory I get.
"Error Domain=NSCocoaErrorDomain Code=513 "You don’t have permission to save the file “variances.csv” in the folder “CSVtest”." UserInfo={NSFilePath=/Users/username/Desktop/CSVtest/variances.csv, NSUnderlyingError=0x600000c9eaf0 {Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"}}"
My ultimate question is about saving a screenshot from an AppleTV application using XCTest and Swift4 (running on a MacBook paired to the TV device), but I'm having trouble even writing a simple text string to a local file. If I can get this simple file-save working, I'm hoping I can resolve the screenshot issue. (Apologies for making this look like two questions but they appear to be related and resulted from my troubleshooting efforts.)
First, here's what I'm trying to do with a screenshot, based on sample code I found somewhere online:
let appshot = XCUIApplication().windows.firstMatch.screenshot()
let shotpath = FileManager.default.urls(for: .downloadsDirectory, in: .userDomainMask)[0].appendingPathComponent("appshot.png")
let shotpathUrl = URL(string: "file://\(shotpath)")
print("Saving to: \(shotpath)")
do {
try appshot.pngRepresentation.write(to: shotpathUrl!)
} catch {
print("Failed saving screenshot due to \(error)")
}
This gives me the following output:
Saving to: file:///var/mobile/Containers/Data/Application/77D52C66-353B-4029-97D5-48E6BAE35C92/Downloads/appshot.png
Failed saving screenshot due to Error Domain=NSCocoaErrorDomain Code=4 "The file “appshot.png” doesn’t exist." UserInfo={NSFilePath=///var/mobile/Containers/Data/Application/77D52C66-353B-4029-97D5-48E6BAE35C92/Downloads/appshot.png, NSUnderlyingError=0x1c405bc60 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}}
Of course, the file doesn't exist because that's the file I'm trying to create. But /var/mobile doesn't exist on my laptop either -- it looks like the path FileManager is building may exist on the AppleTV device, but I want it on my laptop where my test script is executing.
So I backed out to a much more simple case, and even this is giving me problems:
let str = "This is a test"
let path = "file:///Users/haljor/foo.txt"
let pathUrl = URL(string: path)!
print("Path: \(path)")
print("URL: \(pathUrl)")
do {
try str.write(to: pathUrl, atomically: true, encoding: .utf8)
} catch {
print("Caught error writing to \(pathUrl): \(error)")
}
And here's the output:
Path: file:///Users/haljor/foo.txt
URL: file:///Users/haljor/foo.txt
Caught error writing to file:///Users/haljor/foo.txt: Error Domain=NSCocoaErrorDomain Code=4 "The folder “foo.txt” doesn’t exist." UserInfo={NSURL=file:///Users/haljor/foo.txt, NSUserStringVariant=Folder, NSUnderlyingError=0x1c40553f0 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}}
Here, it looks like it's trying to write to a folder at the path I specified, not a file. Clearly there's something I'm not understanding in each of these cases.
I don't really have a preference for whether I use a fully-specified path or something using FileManager -- it just needs to land somewhere on my laptop (not the TV device). What am I missing?
You can add an attachment to the test case and save it to disk too. The problem was that Downloads folder may not exist in the container yet. The best way to handle this is via init-once property:
var downloadsFolder: URL = {
let fm = FileManager.default
let folder = fm.urls(for: .downloadsDirectory, in: .userDomainMask)[0]
var isDirectory: ObjCBool = false
if !(fm.fileExists(atPath: folder.path, isDirectory: &isDirectory) && isDirectory.boolValue) {
try! fm.createDirectory(at: folder, withIntermediateDirectories: false, attributes: nil)
}
return folder
}()
func test() {
let appshot = XCUIScreen.main.screenshot()
let attachment = XCTAttachment(screenshot: appshot)
attachment.lifetime = .keepAlways
self.add(attachment)
// Save to container
let url = downloadsFolder.appendingPathComponent("appshot.png")
try! appshot.pngRepresentation.write(to: url)
}
If you want to view the attachment, right-click on the test case, select Jump to Report and expand the tree. You will see the screenshot eventually:
I am using Xcode 7.3.1 and Swift 2.0. I am using the following code sample:
func writeToResourcesDataDir() {
if let path = NSBundle.mainBundle().pathForResource("TestData", ofType: ".json") {
let str = "Test String"
do {
try str.writeToFile(path, atomically: false, encoding: NSUTF8StringEncoding)
print("writeToFile successful")
} catch {
print("writeToFile failed")
}
} else {
print("Path does not exist")
}
}
Running under Xcode in the see the "writeToFile successful" message.But, also using the simulator, I can display the TestData in the Resources directory and the file does not have the string.I also used a terminal window in Mac to look at the files in the Resources directory and the TestData file is empty (0 bytes).I know I am in the correct Resources directory because there is another file in the directory that has correct data that is used for running the other parts of the program.
I have spent several days now looking at other google entries about data from writeToFile not working and I have tried out every fix or things to try I have found.
Can anyone help?
I added code to accept the boolean return from the call to writeToFile and it returns a false. I'm not sure why a false is returned but the catch isn't invoked.I am not sure how to get the error code that goes with this writeToFile in Swift 2.0.
I am also wondering if this is a write permissions problem.Should I be using the Documents directory instead of the Data directory?
Try something like this. This is swift 2.3 and xcode 8.
let filename = "yourjsonfile"
let documentDirectoryURL = try! NSFileManager.defaultManager().URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true)
let filePath = documentDirectoryURL.URLByAppendingPathComponent(filename)
let fileExist = filePath?.checkResourceIsReachableAndReturnError(nil)
if (fileExist == true) {
print("Found file")
} else {
print("File not found")
}
Appending the .txt file component to the URL path doesn't work:
var error:NSError?
let manager = NSFileManager.defaultManager()
let docURL = manager.URLForDirectory(.DocumentDirectory, inDomain:.UserDomainMask, appropriateForURL:nil, create:true, error:&error)
docURL.URLByAppendingPathComponent("/RicFile.txt") <-- doesn't work
via debugger:
file:///Users/Ric/Library/Developer/CoreSimulator/Devices/
<device id>/data/Containers/Data/Application/<app id>/Documents/
Writing a String using docURL to a file doesn't work because of the missing file name.
Reason (via error):
"The operation couldn’t be completed. Is a directory"
So Question: Why doesn't the following work?
docURL.URLByAppendingPathComponent("/RicFile.txt")
URLByAppendingPathComponent: doesn't mutate the existing NSURL, it creates a new one. From the documentation:
URLByAppendingPathComponent: Returns a new URL made by appending a
path component to the original URL.
You'll need to assign the return value of the method to something. For example:
let directoryURL = manager.URLForDirectory(.DocumentDirectory, inDomain:.UserDomainMask, appropriateForURL:nil, create:true, error:&error)
let docURL = directoryURL.URLByAppendingPathComponent("/RicFile.txt")
Even better would be to use NSURL(string:String, relativeTo:NSURL):
let docURL = NSURL(string:"RicFile.txt", relativeTo:directoryURL)
With the update to the Swift language, the suggested call to manager.URLForDirectory(...) no longer works because the call can throw (an exception). The specific error is "Call can throw, but it is not marked with 'try' and the error is not handled". The throw can be handled with the following code:
let directoryURL: NSURL?
do
{
directoryURL = try manager.URLForDirectory(.DocumentationDirectory,
inDomain: .UserDomainMask, appropriateForURL: nil, create: true)
}
catch _
{
print("Error: call to manager.URLForDirectory(...) threw an exception")
}