I have the following code:
var error : NSError?
var response : NSHTTPURLResponse?
var urlData : NSData = NSURLConnection.sendSynchronousRequest
(
request,
returningResponse: &response,
error: &error
) as NSData
returningResponse takes an instance of NSURLResponse as mentioned in the reference docs.
Im using NSHTTPURLResponse which is a subclass of NSURLResponse. This works fine in Objective-C but I do not know how to write this in Swift because the compiler throws an error on that line.
The error is:
Cannot convert the expression's type 'NSData' to type 'inout NSHTTPURLResponse'
What does this mean? and how to get it right?
The problem is that you are passing a different type than the method is expecting. You should still pass in NSURLResponse. You can cast the type afterwards:
var urlData = NSURLConnection.sendSynchronousRequest
(
request,
returningResponse: &response,
error: &error
)
if let httpResponse = response as? NSHTTPURLResponse {
// Work with HTTP response
}
Also note, the type of urlData can be inferred from the return type of the method. There is no need to specify the type nor convert the result to NSData so I removed both of those.
Related
I'm trying to get the response from the server as NSDictionary instead of NSData, so first I'm using AFNetworking library and the server request these settings to be HTTP not JSON serializer as the following :
self.responseSerializer = AFHTTPResponseSerializer() as AFHTTPResponseSerializer
self.requestSerializer = AFHTTPRequestSerializer() as AFHTTPRequestSerializer
self.requestSerializer.HTTPMethodsEncodingParametersInURI = NSSet(array: ["GET"]) as! Set<String>
self.responseSerializer.acceptableContentTypes = NSSet(objects: "application/json","text/json","text/javascript","text/html") as? Set<String>
Next is when i get the response from the server it comes to be NSData and its because I'm using AFHTTPRequestSerializer() and here is my code :
self.POST(addUserURL, parameters: dictionary, progress: nil, success: { (task, responseObject) -> Void in
print(responseObject)
}) { (task, error) -> Void in
}
Also inside AFNetworking block its not allowed to handle try and catch for NSJSONSerializtion which can be a possible solution but it doesn't work.
Use NSJSONSerialization for that as shown in below code :
do {
let jsonObject = try NSJSONSerialization.JSONObjectWithData(responseObject, options: .AllowFragments) as! NSDictionary
// use jsonObject here
} catch {
print("json error: \(error)")
}
As response that you get from the server doesn't have top level object that is either Array or Dictionary you have to specify custom reading options in that should be used by AFNetworking.
In order to do that you have to set responseSerializer property on an instance of AFURLSessionManager class. You can do it as follows:
let sessionManager = OLFURLSessionManager.init() //you probably want to keep session manager as a singleton
sessionManager.responseSerializer = AFJSONResponseSerializer.serializerWithReadingOptions(.AllowFragments)
//you should use that instance of session manager to create you data tasks
After that you should be able to correctly parse response from the server as follows:
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 am use Swift to call an initializer from objective-c class(JSONModel)
The class contains some initializer:
-(instancetype)initWithString:(NSString*)string error:(JSONModelError**)err;
-(instancetype)initWithString:(NSString *)string usingEncoding:(NSStringEncoding)encoding error:(JSONModelError**)err;
-(instancetype)initWithDictionary:(NSDictionary*)dict error:(NSError **)err;
-(instancetype)initWithData:(NSData *)data error:(NSError **)error;
Since I want to call the initWithDictionary one, I write code like
var error:NSError
var loginRes = RegisterResponse(dictionary: dict , error: &error)
in which , RegisterResponse is a subclass of JSONModel, dict is a pre-used Dictionary variable
However, the complier complains like:
missing argument for parameter "usingEncoding" in call.
It seems that the complier think I am calling the
-(instancetype)initWithString:(NSString *)string usingEncoding:(NSStringEncoding)encoding error:(JSONModelError**)err;
rather than the third one. Are there any solution?
-(instancetype)initWithDictionary:(NSDictionary*)dict error:(NSError **)err;
is mapped to Swift as
init!(dictionary dict: [NSObject : AnyObject]!, error err: NSErrorPointer)
As explained in Adopting Cocoa Design Patterns / Error Reporting,
you have to pass an optional NSError as an in-out expression:
var error : NSError?
let loginRes = RegisterResponse(dictionary: dict, error: &error)
or with error checking:
var error : NSError?
if let loginRes = RegisterResponse(dictionary: dict, error: &error) {
println("success")
} else {
println(error!.localizedDescription)
}
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.)