Error Handling

Question 1

What is error handling?

Answer 1

Error handling is the process of responding to and recovering from error conditions in your program

Question 2

What is an error?

Answer 2

Code that produces an incorrect or unexpected result

Question 3

What are the 4 ways to handle errors in swift?

Answer 3

Propagating the errors using throwing functions.
Handling errors using do-catch
Converting errors to optional values
Disabling Error Propagation

Question 4

How do you propagate errors using throwing functions(show an example)?

Answer 4

You write the throws keyword in the function’s declaration after its parameters 
Func canThrowErrors() throws -> String 
Also need the word throw when selecting what error to throw
(example)

Question 5

How do you test a throwing function?

Answer 5

You have to use the try keyword

example

Question 6

How do you handle errors using do-catch?

Answer 6

If an error is thrown by the code in the do clause, it passes it to catch clause to see what errors the clause can handle.

Question 7

What happens if the catch clause doesn’t have a pattern?

Answer 7

The clause matches any error and binds the error to a local constant named error.

Question 8

How do you convert errors to optional values?

Answer 8

You use try? to handle an error by converting it to an optional value
If an error is thrown while evaluating the try? expression, the value of the expression is nil

Question 9

In what order are defer statements executed?

Answer 9

Reverse order

Question 10

What language construct allows us to easily deal with domain errors in Swift?

Answer 10

Optionals

Question 11

An error that occurs because a result is outside the accepted range of values is known as a

Answer 11

Domain error

Question 12

Errors that are raised before your code is run is commonly known as a:

Answer 12

Compiler error

Question 13

Where do we add the throws keyword to indicate that the function can throw an error?

Answer 13

After the parameter list and before the return type

Question 14

TF: The throw keyword is a control transfer statement and exits the current scope

Answer 14

True

Question 15

To allow an object to model an error, we conform to the ___________ protocol

Answer 15

Error

Question 16

TF: An error is said to occur when you get an incorrect or unexpected result

Answer 16

True

Question 17

TF: By default all functions throw errors

Answer 17

False

Question 18

To call a throwing function we need to mark it with a certain keyword to indicate that this function can return an error. What is the keyword?

Answer 18

Try

Question 19

TF: A catch clauses cannot pattern match on different error cases like a switch statement

Answer 19

False

Question 20

Where are errors thrown from a function handled?

Answer 20

Catch clause

Question 21

The call to a throwing function along with the happy path of code is encapsulated in a _______ clause.

Answer 21

Do

Question 22

To execute statements as we leave the current scope we use a ________ statement

Answer 22

Defer

Question 23

In Swift, you can indicate what kind of error is being thrown from a function, i.e, the function preserves type information of thrown errors.

Answer 23

False, We can only indicate an error is thrown, not the type of error

Question 24

When an error is thrown from inside a do clause, what happens?

Answer 24

The error is propagated to its outer scope and handled by a catch clause.