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iOS Error Handling in Swift 2.0 Error Handling Handling Errors

Jeff Ripke
Jeff Ripke
41,989 Points
Posted by Jeff Ripke
Jeff Ripke
41,989 Points

In the editor, you have a struct named Parser whose job is to deconstruct information from the web. The incoming data ca

I am having a hard time figuring this question out. Not sure what to do next.

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

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

  func parse() throws {
    guard let data = 
  }
}

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

4 Answers

Martin Wildfeuer
PLUS
Martin Wildfeuer
Courses Plus Student 11,071 Points
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

Firstly, we initialize a new instance of parser with a dictionary. Once initialized, we can call the function parse to parse the data.

The function parse will throw an error in one of the following cases:

  1. the dictionary data, an optional, is nil
  2. data does not contain the key "someKey"

The code would be something like this.

func parse() throws {

    // 1. Make sure data is not nil.
    // If it is nil throw an error, otherwise
    // unwrap it to var parsedData
    guard let parseData = data else {
        // This will throw and exit the parse
        // function right away
        throw ParserError.EmptyDictionary
    }

    // 2. Make sure parseData contains key "someKey"
    guard parseData.keys.contains("someKey") else {
        throw ParserError.InvalidKey
    }

    // If no errors are thrown, proceed here...
}

Hope that helps :)

macserwicki
macserwicki
8,072 Points
macserwicki
macserwicki
8,072 Points

You're only missing the "try" keyword on the "parse()" function. You need it because the "parse()" function "throws".

enum ParserError: ErrorType {
    case EmptyDictionary
    case InvalidKey
}

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

    func parse() throws {
        guard let parsedData = data else {
            throw ParserError.EmptyDictionary
        }
        guard parsedData.keys.contains("someKey") else {
            throw ParserError.InvalidKey
        }
    }
}

let data: [String : String?]? = ["someKey": nil]


do {
    let parser = try Parser(data: data)
   try parser.parse()
} catch {

}
Jeff Ripke
Jeff Ripke
41,989 Points
Jeff Ripke
Jeff Ripke
41,989 Points

Thanks for helping that worked. Know I am having a hard time figuring out the second part:

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

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

    func parse() throws {
        guard let parsedData = data else {
            throw ParserError.EmptyDictionary
        }
        guard parsedData.keys.contains("someKey") else {
            throw ParserError.InvalidKey
        }
    }
}

let data: [String : String?]? = ["someKey": nil]


do {
    let parser = try Parser(data: data)
    parser.parse()
} catch ParserError.EmptyDictionary {

}

Thanks,

Jeff

MUZ140734 Tinashe Chibwe
MUZ140734 Tinashe Chibwe
16,960 Points
MUZ140734 Tinashe Chibwe
MUZ140734 Tinashe Chibwe
16,960 Points

my code kept failing until i used dot notation

""" let data: [String : String?]? = ["someKey": nil] do { let parser = try Parser(data: data).parse() } catch let error { print("error") } """