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iOS Error Handling in Swift Error Handling Handling Errors

i can't figure out what i'm doing wrong

i Click recheck work and it tells me to check the preview button for errors. no errors are appearing but it says it won't compile. i'm also using the playground to work out ideas to get no errors.

enum ParserError: Error {
  case emptyDictionary
  case invalidKey

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

  func parse(dict: [String : String?]?) throws {
    guard (dict?.keys.contains("someKey"))! else {
            throw ParserError.invalidKey


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

1 Answer

You should do this in a way that does not require you to force unwrap. The most concise way I've found is below.

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

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