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iOS Error Handling in Swift 2.0 Error Handling Handling Errors

Posted by Alia Khan
Alia Khan
3,733 Points

Error handling swift

Hi Im struggling on the challenge

I know that after the try keyword I have to call the parse function but it wouldn't let me and then I changed the struct brackets to not contain the function and now it lets me use the parse function inside the do clause but it still won't compile and im getting other errors, does anyone know what Ive done wrong

swift_lint.swift:18:19: warning: immutable value 'someKey' was never used; consider replacing with '_' or removing it guard let someKey = data["someKey"] else { ^~~~~~~ _ swift_lint.swift:33:17: error: use of unresolved identifier 'parse' let info = try parse()

error.swift 
enum ParserError: ErrorType {
  case EmptyDictionary
  case InvalidKey
}

struct Parser {
  var data: [String : String?]?

  func parse() throws {

  guard let data = data else {
        throw ParserError.EmptyDictionary

        }

        guard let someKey = data["someKey"] else {

            throw ParserError.InvalidKey


        }


  }
}

let data: [String : String?]? = ["someKey": nil]
let parser = Parser(data: data)

do {
 let info = try parse()

} catch ParserError.EmptyDictionary() {


}
Alia Khan
Alia Khan
3,733 Points

Jennifer Nordell

Alia Khan
Alia Khan
3,733 Points

I did it! who :)

No idea how Im still bit unsure so if anyone can go over the logic it would be helpful

do {
 let dataInfo = try Parser.parse(parser)
} catch ParserError.InvalidKey(let someKey) {
print(someKey)

}

1 Answer

Christopher David
PLUS
Christopher David
Courses Plus Student 20,027 Points
Christopher David
Christopher David
Courses Plus Student 20,027 Points 
do {
 let info = try parse()

} catch ParserError.EmptyDictionary() {

}

do {
 let dataInfo = try Parser.parse(parser)
} catch ParserError.InvalidKey(let someKey) {
print(someKey)

}

The difference in what you did is that you called the instance method from the object when you got it correct. In your first attempt, you tried to call a method from out of the blue - parse() (random method) vs Parser.parse(parser).(method called from object)

Also, I'm not sure because I can't run everything the same in Playground since I am now on Xcode8, but I believe you do not need to set the constant datainfo with let dataInfo = try Parser.parse(parser) since there is no return type to the function/method.

enum ParserError: ErrorType {
  case EmptyDictionary
  case InvalidKey
}

struct Parser {
  var data: [String : String?]?

  func parse() throws {

  guard let dataObject = data else {
    throw ParserError.EmptyDictionary
  }

  guard let keyValue = dataObject["someKey"] else {
    throw ParserError.InvalidKey
  }

  }
}

let data: [String : String?]? = ["someKey": nil]
let parser = Parser(data: data)

do {
  try parser.parse()
} catch let error {
  print("Error occurred")
}

The above is what I ran. As you can see, I did not set parser.parse() to a constant.