Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Error Handling in Swift Error Handling Handling Errors

Mohamed Almulla
Mohamed Almulla
2,506 Points

How do I check if they key exist or is not nil?

I need help writing the guard statement for the key and I don't really understand the hint that we were given that much either. Would be great if someone can tell me what I'm missing. Thank you very much.

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

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

  func parse(from dict: [String: String]) throws -> Parser {
        guard let parse = dict["someKey"] else{
        throw ParserError.emptyDictionary 
    }

    guard let val = dict[keys] else {
        throw ParserError.invalidKey 
    }
  }
}

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

1 Answer

You do not need to create a new constant for this instead you can just check the values.

    func parse() throws {
        guard data?.isEmpty == false else {
            throw ParserError.emptyDictionary
        }

        guard (data?["someKey"]) != nil  else {
            throw ParserError.invalidKey
        }
    }

If this helped you out please remember to mark it as best answer and give it an upvote. Greatly appreciated.