I see many versions of this question, but I've looked through many of them and haven't found something explaining my problem yet. I hope this isn't a repeat question.
I am simply trying to initialize an AVAssetWriter with this init! method defined in the documentation:
init!(URL outputURL: NSURL!,
fileType outputFileType: String!,
error outError: NSErrorPointer)
So I've written the following code in my playground:
var err : NSError? = nil
var outputPath = "\(NSTemporaryDirectory())mypath.mov"
var url = NSURL(fileURLWithPath: outputPath)
var fileManager = NSFileManager.defaultManager()
println("The putput path is \(outputPath)")
if(fileManager.fileExistsAtPath(outputPath))
{
fileManager.removeItemAtPath(outputPath, error: &err)
println(outputPath)
if(err != nil)
{
println("Error: \(err?.localizedDescription)")
}
}
var writeInitErr : NSError? = nil
var assetWriter = AVAssetWriter(URL: url, fileType: AVMediaTypeVideo, error: writeInitErr)
However, the last line throws the error "Extra argument 'URL' in call". None of the solutions I found in other questions about this error seem to apply here. Am I passing the wrong type to the parameter? Am I misunderstanding the use of the initializer?
Well, as is often the case, I figured out the answer minutes after asking the question.
The problem is actually with the "error: writeInitError" parameter, which should be
"error: &writeInitError"
Apparently the xcode error reporting is buggy, and was reporting a problem with the URL parameter instead. Fixing the error parameter solved the problem.
I suppose until the error reporting is improved, "Extra argument in call" translates to "Something is wrong with one of your parameters".
Related
I've been trying to implement try and catch in the following code
if let s = songId {
let track: NSURL!
track = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource(s, ofType: "mp3")!)
.............
}
I came up with the following code:
do {
track = try NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource(s, ofType: "mp3")!)
}
catch let error as NSError {
print("NSURL Error: \(error.localizedDescription)")
}
But I get the following warnings:
No calls to throwing functions occur within 'try' expression
and
'catch' block is unreachable because no errors are thrown in 'do' block
And this is strange to me, because this construction usually works.
Only with NSURL this construction isn't working. And I can't figure out why this is happening. Maybe it has something to do with it being an optional, but im not sure.
I can't figure out how to solve this. I need to use a try/catch or something similar, but I can't figure it out how to make it work.
I saw some similar problems on Google, but it didnt gave me an answer.
So my question is: How can I implement a try/catch construction or something similar with NSURL?
Thanks in advance.
There are no methods used that marked with throws keyword at the definition. So it really does not make much sense to wrap your code with try-catch. I would recommend to consider this:
let s = "song"
guard let trackURL = NSBundle.mainBundle().URLForResource(s, withExtension: "mp3") else {
print("File not found in the app bundle: \(s).mp3")
return false
}
Does it help?
That initializer doesn't fail and doesn't throw or fail so a try/catch block is unnecessary. The declaration is:
public init(fileURLWithPath path: String)
If it could throw an error is would be declared as:
public init(fileURLWithPath path: String) throws
Or if it might fail without throwing an error it would be declared as:
public init?(fileURLWithPath path: String)
If you're certain that the bundle will always contain the track you're looking for then you can just use
let track = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource(s, ofType: "mp3")!)
I am trying to validate different errors while downloading text files from AWS S3, and with the next piece of code:
... above here function receiving String parameters ruta, archivo, archivoLocal
let directorioURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first! as NSURL
let archivoURL = directorioURL.URLByAppendingPathComponent("b\(archivoLocal)")
let downloadRequest = AWSS3TransferManagerDownloadRequest()
downloadRequest.bucket = ruta
downloadRequest.key = archivo
downloadRequest.downloadingFileURL = archivoURL
let transferManager = AWSS3TransferManager.defaultS3TransferManager()
let task = BFTask()
let executor = BFExecutor.mainThreadExecutor()
transferManager.download(downloadRequest).continueWithExecutor(executor, withBlock: { (task) -> AnyObject! in
if task.error != nil {
if task.error.domain == AWSS3TransferManagerErrorDomain {
self.processDomainErrorType(AWSS3TransferManagerErrorType(rawValue: task.error.code))
} else {
self.processError(task.error)
}
} else if task.result != nil {
do {
let mytext = try String(contentsOfURL: archivoURL, encoding: NSUTF8StringEncoding)
self.processResult(mytext)
} catch let urlerror as? NSError {
self.processError(urlerror)
}
}
...
I am getting the error:
Invalid conversion from throwing function of type '(_) throws -> AnyObject!' to non-throwing function type '#convention(block) (BFTask!) -> AnyObject!'
I obtained the "do { try } catch" syntax from https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/AdoptingCocoaDesignPatterns.html#//apple_ref/doc/uid/TP40014216-CH7-ID10
I can remove the error by replacing the catch clause with:
} catch _ {
self.processError(NSError(domain: "String-ContentsOfURL Error", code: 100, userInfo: nil))
}
Of course this way I will never know the real cause why ContentsOfURL could be failing.
All I can figure out why this error happens is because this syntax is valid only for OS X apps and for iOS the error handling guide at
https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html#//apple_ref/doc/uid/TP40014097-CH42
allows only the second syntax unless you own the object throwing the errors from an enum structure of ErrorType type, which is not the case since I want to catch the NSError from String object, contentsOfURL function.
I hope someone could guide me through this, maybe being XCode 7 a beta, the catch syntax is still incomplete or maybe I should not matter about the reason why this function fails, but I think it is important to determine what is making this function fail and if it could be traced and fixed before reaching the do-try-catch clause.
Additionally to the above error, I am getting a warning in the task variable assignation line to BFTask() saying that "Initialization of immutable value 'task' was never used". I think this is a bug with this beta version that it doesn't include the pattern to acknowledge that the variable task is being used in the asynchronous block. I'd appreciate a lot some confirmation about this and if I just need to ignore it.
By the way, the only reason I am using XCode 7 beta is because my client wants to evaluate the app before acquiring their apple membership.
Apple replaced NSError with ErrorType in Swift 2.
Replace your own explicit usage of NSError with ErrorType and you don't get this type of compiler errors.
Hi i try to find a way to parse JSON in SWIFT, this works great for me but i run into a problem.
I let the user enter a username that is used for the JSON URL -> if the user type in a valid username all works fine.
But if he enter a wrong username my parsing fails, this is correct too, but for now my app only crashes and i looking for a way to make a work around.
This is my Code where it crashes,
let url0 = NSURL(string: newUrlPath!)
let session0 = NSURLSession.sharedSession()
let task0 = session0.dataTaskWithURL(url0!, completionHandler: {data, response, error -> Void in
if (error != nil) {
println(error)
} else {
let summonorID_JSON = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
The Xcode Error
Error Domain=NSURLErrorDomain Code=-1002 "The operation couldn’t be
completed. (NSURLErrorDomain error -1002.)" UserInfo=0x7c12d610
{NSErrorFailingURLKey=XX, NSErrorFailingURLStringKey=XX,
NSUnderlyingError=0x7c12c8d0 "The operation couldn’t be completed.
(kCFErrorDomainCFNetwork error -1002.)"} fatal error: unexpectedly
found nil while unwrapping an Optional value
All is fine cause this is the return page i get from my Request
https://br.api.pvp.net/api/lol/br/v1.4/summoner/by-name/smirknaitiax?api_key=5c7d4d4f-f320-43d5-8647-643c9f6ee5de
And yes he can't parse this into a NSDirectory as its no JSON that returns (as its normally is) is there a way to take care that if this page comes up (so the user entered a wrong username) that i can exit my loop/take a other way ;)?
You are using many operations which could all fail, and Swift is quite unforgiving about failure. Your code will crash if newURLPath is nil, if url0 is nil because newURLPath wasn't a valid URL.
So your URL request might return an error (the request itself failed), but you have the case that the URL request succeeded but gives unexpected results (not a JSON dictionary). Your code ending in "as NSDictionary" tells Swift: "I know I might not get a dictionary, but convert what you get to a dictionary and crash if this doesn't work". Just change this to
if let parsedJSON = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil)
{
// Will still crash if the server sends a valid JSON array
let summonorID_JSON = parsedJSON as NSDictionary
}
else
{
// data wasn't valid JSON, handle it.
}
The difference is that the optional value returned by the JSON parser will be accepted without crashing, and you check whether you received valid JSON or not.
Since you are getting 404 on this request, I assume that this will happen every time something is bad with username, you should handle server response to fit that. First thing will be to check what server returned:
let httpResp: NSHTTPURLResponse = response as NSHTTPURLRespons
At this point you can access statusCode property, that will tell you if request was good or not (404). Having that information you can decide what to do, and for example, you can modify your code something like this:
let url0 = NSURL(string: newUrlPath!)
let session0 = NSURLSession.sharedSession()
let task0 = session0.dataTaskWithURL(url0!, completionHandler: {data, response, error -> Void in
if (error != nil) {
println(error)
} else {
let httpResp: NSHTTPURLResponse = response as NSHTTPURLRespons
httpResp.statusCode != 404 {
let summonorID_JSON = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
} else {
// Handle error at this point, tell user to retype username etc.
}
})
NSURL is a failable initializer and exactly this happens when you give an invalid url: It fails to initialize.
So wrap your code in an conditional unwrap:
if let url0 = NSURL(string: newUrlPath!) {
...
}
The url0 becomes nil if user enter wrong data. If you use the nil value as url0! app will crash.
When you add a ! after a variable you tell the compiler the value will not be nil.
so to avoid the crash, you have to check for nil condition before calling
let task0 = session0.dataTaskWithURL(url0!, completionHandler: {data, response, error -> Void in
I commonly see a pointer to an optional error variable being used, just like in this block of code:
if fileManager.fileExistsAtPath(path)
{
var error: NSError?
if !fileManager.removeItemAtPath(path, error: &error)
{
println("Error removing the file : \(error)")
}
}
Why do we do this?
The error parameter is an inout parameter, and can set the value of error rather than returning it from the function. Look up "inout" in Apple's iBook on Swift.
I am trying to mimic the app as in this youtube tutorial, but using Swift and I am facing a problem constructing the closure as shown in the code snippet below.
func twitterTimeline() {
let account = ACAccountStore()
let accountType = account.accountTypeWithAccountTypeIdentifier(ACAccountTypeIdentifierTwitter)
// take action
account.requestAccessToAccountsWithType(accountType, options: nil,
completion: { (granted, error) in
if (granted) {
// invoke twitter API
let arrayOfAccount: NSArray = account.accountsWithAccountType(accountType)
if (arrayOfAccount.count > 0) {
let twitterAccount = arrayOfAccount.lastObject as ACAccount
let requestAPI = NSURL.URLWithString("http://api.twitter.com/1.1/atuses/user_timeline.json")
var parameters = Dictionary<String, String>()
parameters["100"] = "count"
parameters["1"] = "include_entities"
let posts = SLRequest(forServiceType: SLServiceTypeTwitter, requestMethod: SLRequestMethod.GET, URL: requestAPI, parameters: parameters)
posts.account = twitterAccount
// This is the Error Prone Area
let handler: SLRequestHandler = { (response, urlResponse, error) in
self.array = NSJSONSerialization.JSONObjectWithData(data: response, options: NSJSONReadingOptions.MutableLeaves, error: &error) as NSArray
}
posts.performRequestWithHandler(handler)
}
} else {
// do something
}
}
)
}
The error I get is
Cannot convert expression's type '($T1, $T2, $T3) -> $T0' to type '()'
I have tried checking and explicitly casting the types with no much help. I believe the error is somewhere else. Could anyone help me with what exactly is the trouble? I am sorry, if this turns out to be a näive question.
Thanks in advance,
Nikhil
This looks like an interesting case of error propagation in the compiler — I'd suggest filing a bug report with Apple.
The error message you're getting says that you can't assign a closure (which takes three parameters and returns one value) to something that takes no parameters. What's actually going wrong is that the handler closure you're defining takes its error input parameter and tries to pass it to JSONObjectWithData(_:options:error:). That's problematic from a language perspective because the error you're getting in is an immutable (optional) reference to one error, and the parameter you're passing it to expects a mutable pointer for it to (potentially) write another error into.
It's also incorrect API usage. The error you receive as a parameter in the closure is a report of an error that happened in whatever procedure calls your closure. You should log this error, present it to the user, or examine it so your app can gracefully fail. The error parameter you pass to JSONObjectWithData is a place for you to receive reports of additional errors that occur when decoding JSON from your data — you should be handling this error, too. These are two separate places to receive errors, so you shouldn't be passing one to the other.
If you fix that, you'll find a more helpful compiler message saying that the data: label on the first parameter to that function should be omitted. Also, you can use type inference for the options: parameter. So, your handler definition should look something more like this:
let handler: SLRequestHandler = { (response, urlResponse, error) in
// check for error and do something about it if need be, then...
var err: NSError?
if let jsonArray = NSJSONSerialization.JSONObjectWithData(response, options: NSJSONReadingOptions.MutableLeaves, error: &err) as? NSArray {
self.array = jsonArray
} else {
// do something about err
}
}
(You can also probably use a Swift typed array instead of an NSArray if you know what to expect from your JSON. But that's another subject for another question. Actually, several questions.)