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Test: Swift - Nil Coalescing Operator
4. var vowels = [0:”a”, 1:”e”, 2:”i”, 3:”o”, 4:”u”]; var vowel = vowels[5] ?? “a” - What’s in vowel?
Results Congratulations! Correct Answer. You Answered: None. If you took the test, your answer will show up here. Correct Answer: a Explanation In this case, the vowels variable is a dictionary. Dictionary will return nil, if it cannot find the key that is being searched. When ?? sees a nil, it will return the default value provided to it - a in this case. Dictionaries behave differently from Arrays here — if an index is out of range, it would be a fatal error in case of an Array.Take the Test Take the complete test on this topic. You will be able to review answers to questions and get a test score.
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This article talks about the Nil Coalescing Operator (??) in Swift.
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Test on Nil Coalescing Operator for Optionals.
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