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iOS Error Handling in Swift 2.0 Error Handling Handling Errors

Posted by David Yoo
David Yoo
6,889 Points

I'm stuck on this one.

What am I missing here?

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

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

  func parse() throws {
    if data == nil {
      throw ParserError.EmptyDictionary
    }
    if data!.keys.contains("someKey") {
      throw ParserError.InvalidKey
    }

  }
}

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

2 Answers

Steven Deutsch
Steven Deutsch
21,046 Points
Steven Deutsch
Steven Deutsch
21,046 Points

Hey David Yoo,

I answered this question previously. You can check out my response here: https://teamtreehouse.com/community/error-handling-2

However, I would make one change to my code as recommended by a comment in this thread. Instead of using guard let to unwrap the parser data, we should just do a guard on the data to make sure it is != to nil. This is because we will never be using the value, so it is pointless to bind it to a constant if it will never be used.

Good Luck

jcorum
jcorum
71,830 Points
jcorum
jcorum
71,830 Points

You can also do it this way:

    func parse() throws {
        guard let data = data else {
            throw ParserError.EmptyDictionary
        }

        guard let key = data["someKey"] else {
            throw ParserError.InvalidKey
        }
    }