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iOS Error Handling in Swift 2.0 Error Handling Handling Errors

Posted by vikashkhanna
vikashkhanna
Courses Plus Student 586 Points

compiler is not able to detect the error in the code

enum ParserError: ErrorType { case EmptyDictionary case InvalidKey }

struct Parser{ var data: [String : String?]? func parse() throws { guard (data?.keys) != nil else { throw ParserError.EmptyDictionary } guard data?.keys.contains("someKey") != nil else { throw ParserError.InvalidKey } } }

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

do{ parser.data = data try parser.parse() }catch ParserError.InvalidKey{ print("Invalid Key") }

error.swift 
enum ParserError: ErrorType {
    case EmptyDictionary
    case InvalidKey
}


struct Parser{
    var data: [String : String?]?
    func parse() throws {
        guard (data?.keys) != nil else {
            throw ParserError.EmptyDictionary
        }
        guard data?.keys.contains("someKey") != nil else {
            throw ParserError.InvalidKey
        }
    }
}


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


do{
    parser.data = data
 try parser.parse()
}catch ParserError.InvalidKey{
    print("Invalid Key")
}

1 Answer

Roberto Pando
Roberto Pando
9,486 Points
Roberto Pando
Roberto Pando
9,486 Points

Really close, first you're checking if data is completely empty and you can do that by trying to unwrap it, secondly it wants to know if data contains a key named someKey, no need to check if is nil you probably got confused and tried to check that the key someKey was not empty: Your code:

 func parse() throws {
        guard (data?.keys) != nil else {
            throw ParserError.EmptyDictionary
        }
        guard data?.keys.contains("someKey") != nil else {
            throw ParserError.InvalidKey
        }
    }

changed to:

 func parse() throws {
        guard let data = data else {
            throw ParserError.EmptyDictionary
        }

        guard data.keys.contains("SomeKey") else {
            throw ParserError.InvalidKey
        }
    }

After that you just need to exhaust the errors by adding a catch block for .EmptyDictionary