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iOS Error Handling in Swift 2.0 Error Handling Handling Errors

Will Van de Walle
Will Van de Walle
2,352 Points
Posted by Will Van de Walle
Will Van de Walle
2,352 Points

Overall really confused

This code really doesn't help much, as I haven't made any changes, but I am confused as to what the syntax for this challenge is. I am digging around, but do I use guard let? Or if? Please help.

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

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

  func parse() throws {

  }
}

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

2 Answers

Jhoan Arango
Jhoan Arango
14,575 Points
Jhoan Arango
Jhoan Arango
14,575 Points

Hello :

There are different ways of doing it.. you can use guard, or you can you if let. But I recommend guard, since it cleaner, and its always good to exit the function early. 

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

    // Here we indicate that this method, can throw an error
    func parse() throws {
        // The guard is used as a way to check if there is an error, and if there is, what type of error is it
        guard let data = data else {
            throw ParserError.EmptyDictionary
        }

        // This guard checks if the key exist, and it throws the type of error "invalidKey" if it does not.
        guard let key = data["someKey"] else {
            throw ParserError.InvalidKey
        }
    }
}

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

Hope this helps you a bit.

Good luck

Christian McMullin
Christian McMullin
13,086 Points
Christian McMullin
Christian McMullin
13,086 Points

the challenge says to use the contains method to check for "someKey"

enum ParserError: ErrorType {
    case EmptyDictionary
    case InvalidKey
}

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

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

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