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iOS Error Handling in Swift Error Handling Handling Errors

Gavin Butler
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Gavin Butler
iOS Development with Swift Techdegree Graduate 15,489 Points

If the key does not exist, make sure to throw the InvalidKey error

I get the above error and nothing in the output file when I use the following code in "Error Handling in Swift/Handling Errors/Task 1 of 3":

guard data != nil else { throw ParserError.emptyDictionary } guard let exists = data?.keys.contains("someKey") else { throw ParserError.invalidKey } guard let keyVal = data?["someKey"] else { throw ParserError.emptyDictionary }

I'm not sure what I'm doing wrong here. Also, is there a better way to write this given that the compiler is telling me that I don't use the 'exists' and 'keyVal' constants?

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

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

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

let data: [String : String?]? = ["someKey": nil]
let parser = Parser(data: data)
Gavin Butler
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.a{fill-rule:evenodd;}techdegree seal-36
Gavin Butler
iOS Development with Swift Techdegree Graduate 15,489 Points

Didn't realize that the nil was wrapped as Optional(nil). Solved it with the following code, but think it could be written much better somehow. guard data != nil else { throw ParserError.emptyDictionary } guard true == data?.keys.contains("someKey") else { throw ParserError.invalidKey } if let val = data?["someKey"] { guard val != nil else { throw ParserError.emptyDictionary } }

1 Answer

Gavin Butler
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Gavin Butler
iOS Development with Swift Techdegree Graduate 15,489 Points

Didn't realize that the nil was wrapped as Optional(nil). Solved it with the following code, but think it could be written much better somehow. guard data != nil else { throw ParserError.emptyDictionary } guard true == data?.keys.contains("someKey") else { throw ParserError.invalidKey } if let val = data?["someKey"] { guard val != nil else { throw ParserError.emptyDictionary } }