Try? for optional result in Swift - Cheat Sheet & Quick Revision

Recall & Review

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What does try? do in Swift?

try? attempts to run a function that can throw an error. If the function succeeds, it returns an optional with the result. If it throws an error, it returns nil instead of crashing.

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How is try? different from try!?

try? returns an optional and safely handles errors by returning nil. try! forces the call and crashes if an error is thrown.

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What type does a function call with try? return?

It returns an optional type wrapping the function's return type. For example, if the function returns Int, try? returns Int?.

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Example: What is the output of <code>let result = try? Int("123")</code>?

The output is Optional(123) because the string "123" can be converted to an integer successfully.

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Example: What happens with <code>let result = try? Int("abc")</code>?

The output is nil because "abc" cannot be converted to an integer, so the error is caught and nil is returned.

What does try? return if the function throws an error?

A The function's normal return value

B The error itself

C It crashes the program

D nil

try? returns nil when an error is thrown, preventing a crash.

Which of these is true about try? in Swift?

A It converts errors into optional nil values

B It forces the program to crash on error

C It ignores errors silently and returns a default value

D It throws errors without catching them

try? converts thrown errors into nil optionals safely.

If a function returns String, what type does try? return?

A String?

B Optional<String>

C Both A and C

D String

In Swift, String? is shorthand for Optional<String>. So both are correct.

What happens if you use try! and the function throws an error?

A The program crashes

B It returns nil

C It returns an optional

D It ignores the error

try! forces the call and crashes if an error is thrown.

Which keyword safely handles errors by returning an optional?

A catch

B try?

C try

D try!

try? safely handles errors by returning an optional result.

Explain how try? works in Swift and when you might use it.

Think about how to avoid crashes but still get a result or nil.

Compare try? and try! in Swift. What are the risks and benefits of each?

Consider what happens when an error is thrown.