How to pass an Error up the stack trace in Swift

Question

In java, if one method throws an error, the method that calls it can pass it on to the next method.

public void foo() throws Exception {
     throw new Excep         


        

Answer 1

Referring to Swift - Error Handling Documentation, you should:

1- Create your custom error type, by declaring enum which conforms to Error Protocol:

enum CustomError: Error {
    case error01
}

2- Declaring foo() as throwable function:

func foo() throws {
    throw CustomError.error01
}

3- Declaring bar() as throwable function:

func bar() throws {
    try foo()
}

Note that although bar() is throwable (throws), it does not contain throw, why? because it calls foo() (which is also a function that throws an error) with a try means that the throwing will -implicitly- goes to foo().

To make it more clear:

4- Implement test() function (Do-Catch):

func test() {
    do {
        try bar()
    } catch {
        print("\(error) has been caught!")
    }
}

5- Calling test() function:

test() // error01 has been caught!

As you can see, bar() automatically throws error, which is referring to foo() function error throwing.