1.13 Error Handling

Swift handles errors in a similar way to other languages, but with a few differences. There are 4 main keywords:

throws - this keyword is added to a function to indicate it can throw an error. E.g.

func canThrowAnError() throws {
    // this function may or may not throw an error
}

do - This creates a new scope in which multiple statements which can throw errors can be placed. These are then handled by...
catch - These blocks contain code for handling errors.
try - This keyword is placed before calling functions which can throw errors in a do block.

The do, catch and try are used as follows:

do {
    try canThrowAnError()
    // no error was thrown
} catch {
    // an error was thrown
}

Putting it all together:

func makeASandwich() throws {
    // ...
}
 
do {
    try makeASandwich()
    eatASandwich()
} catch SandwichError.outOfCleanDishes {
    washDishes()
} catch SandwichError.missingIngredients(let ingredients) {
    buyGroceries(ingredients)
}

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