This should be simple and obvious but try catch in swift2 frustrating me. here is my code.
#IBAction func btnAdd_TouchDown(sender: AnyObject) {
do { try AddNewNotesToList() } catch{
if(Ex.UnknownError != "")
{
Error(Ex.UnknownError)
}
}
}
func AddNewNotesToList() throws
{
var obj: TreatmentNotesDTO = TreatmentNotesDTO()
obj.therapist_id = Int(TherapistId)! // getting error here
return
}
Error:
fatal error: unexpectedly found nil while unwrapping an Optional value
Debugger should go to catch but its breaking up. I am from c# and just started swift2. Any help
I would suggest you to use guard to catch such errors:
guard let therapistID = Int(TherapistId) else {
print(TherapistId + " cannot be converted to an Int")
return
// or mark function as throws and return an error
throw NSError(domain: TherapistId + " cannot be converted to an Int", code: 0, userInfo: nil)
}
obj.therapist_id = therapistID
Note that Int(TherapistId)! doesn't throw an error with throws. It is a fatal error which stops program execution.
Related
How to test wether a function in Swift 2.0 throws or not? How to assert that the correct ErrorType is thrown?
EDIT: Updated the code for Swift 4.1 (still valid with Swift 5.2)
Here's the latest Swift version of Fyodor Volchyok's answer who used XCTAssertThrowsError:
enum MyError: Error {
case someExpectedError
case someUnexpectedError
}
func functionThatThrows() throws {
throw MyError.someExpectedError
}
func testFunctionThatThrows() {
XCTAssertThrowsError(try functionThatThrows()) { error in
XCTAssertEqual(error as! MyError, MyError.someExpectedError)
}
}
If your Error enum has associated values, you can either have your Error enum conform to Equatable, or use the if case statement:
enum MyError: Error, Equatable {
case someExpectedError
case someUnexpectedError
case associatedValueError(value: Int)
}
func functionThatThrows() throws {
throw MyError.associatedValueError(value: 10)
}
// Equatable pattern: simplest solution if you have a simple associated value that can be tested inside 1 XCTAssertEqual
func testFunctionThatThrows() {
XCTAssertThrowsError(try functionThatThrows()) { error in
XCTAssertEqual(error as! MyError, MyError.associatedValueError(value: 10))
}
}
// if case pattern: useful if you have one or more associated values more or less complex (struct, classes...)
func testFunctionThatThrows() {
XCTAssertThrowsError(try functionThatThrows()) { error in
guard case MyError.associatedValueError(let value) = error else {
return XCTFail()
}
XCTAssertEqual(value, 10)
// if you have several values or if they require more complex tests, you can do it here
}
}
At least of Xcode 7.3 (maybe earlier) you could use built-in XCTAssertThrowsError():
XCTAssertThrowsError(try methodThatThrows())
If nothing is thrown during test you'll see something like this:
If you want to check if thrown error is of some concrete type, you could use errorHandler parameter of XCTAssertThrowsError():
enum Error: ErrorType {
case SomeExpectedError
case SomeUnexpectedError
}
func functionThatThrows() throws {
throw Error.SomeExpectedError
}
XCTAssertThrowsError(try functionThatThrows(), "some message") { (error) in
XCTAssertEqual(error as? Error, Error.SomeExpectedError)
}
Given the following functions and declarations:
enum SomeError: ErrorType {
case FifthError
case FirstError
}
func throwingFunction(x: Int) throws {
switch x {
case 1:
throw SomeError.FirstError
case 5:
throw SomeError.FifthError
default:
return
}
}
This function will throw a FifthError if 5 is given to the function and FirstError if 1 is given.
To test, that a function successfully runs the unit test could look as follows:
func testNotError() {
guard let _ = try? throwingFunction(2) else {
XCTFail("Error thrown")
return
}
}
The let _ may also be replaced by any other name, so you can further test the output.
To assert that a function throws, no matter what ErrorType the unit test could look like this:
func testError() {
if let _ = try? throwingFunction(5) {
XCTFail("No error thrown")
return
}
}
If you want to test for a specific ErrorType it's done with a do-catch-statement. This is not the best way compared to other languages.
You have to make sure that you...
return in the catch for the correct ErrorType
XCTFail() and return for all other catch
XCTFail() if no catch is executed
Given this requirements a test case could look like this:
func testFifthError() {
do {
try throwingFunction(5)
} catch SomeError.FifthError {
return
} catch {
XCTFail("Wrong error thrown")
return
}
XCTFail("No error thrown")
}
Swift 4.1 Error throwing Test for associated values
enum ParseError: Error, Equatable {
case unexpectedArgument(String)
}
func testWithNoSchemaButWithOneArgument() {
XCTAssertThrowsError(try Args(withSchema: "", andArguments: ["-x"])) { error in
XCTAssertEqual(error as? ParseError, ParseError.unexpectedArgument("Argument(s) -x unexpected."))
}
}
You can use this function:
func XCTAssertThrowsError<T, E: Error & Equatable>(
_ expression: #autoclosure () throws -> T,
error: E,
in file: StaticString = #file,
line: UInt = #line
) {
var thrownError: Error?
XCTAssertThrowsError(
try expression(),
file: file,
line: line) {
thrownError = $0
}
XCTAssertTrue(
thrownError is E,
"Unexpected error type: \(type(of: thrownError))",
file: file,
line: line
)
XCTAssertEqual(
thrownError as? E,
error,
file: file,
line: line
)
}
Example:
XCTAssertThrowsError(try funcThatThrowsSpecificError(), error: SpecificErrorEnum.someError)
I have tried the conversion tools to update these few lines of code, but unfortunately the process did not caught up these two errors.
Could you help me to understand if I need to introduce the do { and error handling? (I am new to swift!).
The error message I receive is the following: "Call can throw, but it is not marked with 'try' and the error is not handled"
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
query.findObjectsInBackgroundWithBlock {(result: [PFObject]?, error: NSError?) -> Void in
self.posts = result as? [Post] ?? []
// 1
for post in self.posts {
// 2
let data = post.imageFile?.getData() --> this is where I get the error message
// 3
post.image = UIImage(data: data!, scale:1.0)
}
self.tableview.reloadData()
}
Insted of this: let data = post.imageFile?.getData()
Use this instead:
do
{
try let data = post.imageFile?.getData()
}
catch
{
print("Error: \(error)")
//Handle the error instead of print probably
}
HI i am a little confused about how to transfer if_else error handling to do try catch successfully.
Here is my code.
let error : NSError?
if(managedObjectContext!.save()) {
NSNotificationCenter.defaultCenter().postNotificationName("updateUndoState", object: nil)
if error != nil {
print(error?.localizedDescription)
}
}
else {
print("abort")
abort()
}
and now i converted to swift 2.0 like this
do {
try managedObjectContext!.save()
}
catch {
NSNotificationCenter.defaultCenter().postNotificationName("updateUndoState", object: nil)
print((error as NSError).localizedDescription)
}
I am confused about where to print abort and do the abort() function
Any idea~? Thanks a lot
Rewriting your code to work the same as your original code
do {
try managedObjectContext!.save()
//this happens when save did pass
NSNotificationCenter.defaultCenter().postNotificationName("updateUndoState", object: nil)
//this error variable has nothing to do with save in your original code
if error != nil {
print(error?.localizedDescription)
}
}
catch {
//this happens when save() doesn't pass
abort()
}
what you probably want to write is the following:
do {
try managedObjectContext!.save()
//this happens when save did pass
NSNotificationCenter.defaultCenter().postNotificationName("updateUndoState", object: nil)
}
catch let saveError as NSError {
//this happens when save() doesn't pass
print(saveError.localizedDescription)
abort()
}
Everything within do {} is good, everything within catch {} is bad
do {
try managedObjectContext!.save()
NSNotificationCenter.defaultCenter().postNotificationName("updateUndoState", object: nil)
}
catch let error as NSError {
print(error.localizedDescription)
abort()
}
use either the error handling or the abort() statement
I'm using the SODA Client for swift (Created by Socrata), I just updated to XCode 7 and swift 2 and found some troubles. The one I haven't been able to solve is the completion handler case when it finds an error, it's not accepting the line "syncCompletion(.Error (reqError))" that supposedly should get the error and return to main thread.
I've seen many errors with the same description here "Type of expression is ambiguous without more context", but not in completion handlers, I saw one using do - catch that is different. I'm don't know enough of swift to find out the way to change this.
Some answers suppose you should rewrite the code because some types could have change in swift 2, but I wouldn't know where to start rewriting.
Thanks in advance for your help.
var task = session.dataTaskWithRequest(request, completionHandler: { data, response, reqError in
// We sync the callback with the main thread to make UI programming easier
let syncCompletion = { res in NSOperationQueue.mainQueue().addOperationWithBlock { completionHandler (res) } }
// Give up if there was a net error
if reqError != nil {
syncCompletion(.Error (reqError))
return
}
// Try to parse the JSON
// println(NSString (data: data, encoding: NSUTF8StringEncoding))
var jsonError: NSError?
var jsonResult: AnyObject!
do {
jsonResult = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers)
} catch var error as NSError {
jsonError = error
jsonResult = nil
} catch {
fatalError()
}
if let error = jsonError {
syncCompletion(.Error (error))
return
}
// Interpret the JSON
if let a = jsonResult as? [[String: AnyObject]] {
syncCompletion(.Dataset (a))
}
else if let d = jsonResult as? [String: AnyObject] {
if let e : AnyObject = d["error"] {
if let m : AnyObject = d["message"] {
syncCompletion(.Error (NSError(domain: "SODA", code: 0, userInfo: ["Error": m])))
return
}
}
syncCompletion(.Dataset ([d]))
}
else {
syncCompletion(.Error (NSError(domain: "SODA", code: 0, userInfo: nil)))
}
})
Solved, I replaced:
if reqError != nil
With
if let error = reqError
and:
syncCompletion(.Error (reqError))
with
syncCompletion(.Error (error))
I am trying to run the query to get object in background with ID but when I run the method query.getObjectInBackgroundWithId , I am getting the error message:
"Cannot invoke 'getObjectInBackgroundWithId' with an argument list of type (string, block: (PFObject!,NSError?) -> Void"
The same thing happens when I use user.signUpInBackgroundWithBlock so I'm thinking maybe Xcode updated some of the features while using 'block's and now maybe the syntax is different? Any ideas?
Here's a snippet of my code:
http://imgur.com/1CvfhbU
YES!!! Thank you!
The new sample code for getObject is:
query.getObjectInBackgroundWithId("Oaq79bhv53") {
(gameScore: PFObject?, error: NSError?) -> Void in
if error == nil && gameScore != nil {
println(gameScore)
} else {
println("error")
}
}
I figured it out!
user.signUpInBackgroundWithBlock{(succeeded: Bool, signUpError: NSError?) -> Void in
Swift 4.2:
query.getObjectInBackground(withId: "YourId") { (gameScore, error) in
if error == nil {
// Success!
print(gameScore)
} else {
// Fail!
}
}