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iOS Error Handling in Swift Error Handling Handling Errors

Posted by Sean Keating
Sean Keating
Courses Plus Student 3,497 Points

Where did I go Wrong. I doing fine its telling me "Make sure you're calling the parse method!" but [someKey] ...

guard let key = !data["someKey"] is coming up wrong?

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

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

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


        let data: [String : String?]? = ["someKey": nil]
do {
    let parse() = try Parser(data : data)
        try parser.parse()

} catch ParserError.emptyDictionary {
 print("type something") // deals with the empty dictionary
} 
catch 
    ParserError.invalidKey {
        print("wrong key")  // deals with invalid key
}
nicholasdevereaux
nicholasdevereaux
16,353 Points
nicholasdevereaux
nicholasdevereaux
16,353 Points

It looks like you moved the parser constant that was provided to the "do" block. Now you're using "try" twice...once to initialize a Parser struct and another to call parse(). Remove your first try statement and put back the constant "parser" that was provided with the question and it should work.

enum ParserError: Error {
  case emptyDictionary
  case invalidKey
}

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

  func parse() throws {
        guard let data = data else {
        throw ParserError.emptyDictionary 
    }
    let keys = data.keys
    if !keys.contains("someKey") {
        throw ParserError.invalidKey
    }
  }
}

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

do {
    let validData = try parser.parse()
} catch {
  print("Error: \(error)")
}

1 Answer

Sean Keating
PLUS
Sean Keating
Courses Plus Student 3,497 Points
Sean Keating
Sean Keating
Courses Plus Student 3,497 Points

Thanks I did try twice! Happy Holidays!