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iOS Error Handling in Swift Error Handling Handling Errors

Sam Belcher
Sam Belcher
3,719 Points
Posted by Sam Belcher
Sam Belcher
3,719 Points

Handling Errors Challenge Swift

Hi, I rewatched the videos a bunch of times but I still don't understand the challenge.

error.swift 
enum ParserError: Error {
  case emptyDictionary
  case invalidKey
}

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

  func parse() throws {

  }
}

let data: [String : String?]? = ["someKey": nil]
let parser = Parser(data: data)
Amazon Web
.a{fill-rule:evenodd;}techdegree
Amazon Web
iOS Development Techdegree Student 4,092 Points 
func parse() throws {
    guard let data = data else { throw ParserError.emptyDictionary }
    guard let key = data["someKey"] else { throw ParserError.invalidKey }
}

First, you need to unwrap the data so that you will know if the has values in it. Then you need to check if someKey has value using guard let or if let statement.

1 Answer

Maria Te
Maria Te
8,521 Points
Maria Te
Maria Te
8,521 Points

I agree with that but a more effective way is:

func parse() throws {
    guard let data = data else { throw ParserError.emptyDictionary }
    guard data["someKey"]  != nil else { throw ParserError.invalidKey }
}

See, when I followed your code, Xcode sent a warning saying that making a new constant could be fixed to a more effective answer. So I changed it to this code and everything seemed perfect. Hope that this helps! :-D