[Solved] You have a dictionary of user IDs to optional email addresses:let emails: [Int: String?] = [1: "a@example.com", 2: nil, 3: "c@example.... | Swift

Swift - Optionals

You have a dictionary of user IDs to optional email addresses:

let emails: [Int: String?] = [1: "a@example.com", 2: nil, 3: "c@example.com"]

How can you safely create a new dictionary mapping user IDs to non-optional emails, excluding users without emails?

AUse mapValues and force unwrap all emails

BUse compactMapValues to unwrap and filter nil values

CUse filter to remove nil emails but keep optionals

DUse flatMap to flatten the dictionary

Step-by-Step Solution

Solution:

Step 1: Understand dictionary with optional values
Values are optional strings; some are nil and should be excluded.
Step 2: Use compactMapValues
This method unwraps optionals and removes entries with nil values, producing non-optional values.
Final Answer:
Use compactMapValues to unwrap and filter nil values -> Option A
Quick Check:
compactMapValues unwraps and filters nil = B [OK]

Quick Trick: compactMapValues unwraps optionals and drops nils [OK]

Common Mistakes:

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