Swift Error Handling - A Better Way

SwiftErrorHandling.swift

//: Playground - noun: a place where people can play

// 1. Proposed Error Handling
enum Error: ErrorType {
    case IsNegative(String)
    case IsPositive(String)
}

func isZero(number: Int) -> Error? {
    if number != 0 {
        if number > 0 {
            return Error.IsPositive("\(number) is positive!")
        } else {
            return Error.IsNegative("\(number) is negative!")
        }
    }
    return nil	// success
}

// 2. Return Result Cases Wrapper
enum IsZeroResult<T> {
    case Success(T)
    case Failure(Error)
}

func isZero_2(number: Int) -> IsZeroResult<Bool> {
    if let err = isZero(number) {
        return IsZeroResult.Failure(err)
    }
    // return Result.Success(T)
    return IsZeroResult.Success(true)
}

// 3. Do-try-catch Error Handling Wrapper
func isZero_3(number: Int) throws {
    if let err = isZero(number) {
        throw err
    }
}

// Implementation
let number = 1

// 1.
if let err = isZero(number) {
    switch err {
    case .IsNegative(let message):
        print(message)
    case .IsPositive(let message):
        print(message)
    }
}

// 2.
switch isZero_2(number) {
case .Failure(let err):
    switch err {
    case .IsNegative(let message):
        print(message)
    case .IsPositive(let message):
        print(message)
    }
case .Success(let bool):
    break
}

// 3.
do {
    try isZero_3(number)
} catch let err as Error {
    switch err {
    case .IsNegative(let message):
        print(message)
    case .IsPositive(let message):
        print(message)
    }
}