Swift Sorting

🔃 Swift Sorting – Complete Beginner to Advanced Guide (With Examples & Output)

Sorting is a core operation in Swift, used for arrays, custom objects, and performance-critical code.
This guide covers basic → advanced sorting, exactly what’s asked in interviews and real projects.

1️⃣ Basic Sorting (sorted vs sort) ⭐

sorted() → returns a new array

Output

sort() → sorts in place

Output

📌 Interview tip

• sorted() → immutable arrays

• sort() → mutable arrays (var)

2️⃣ Descending Order ⭐

Output

3️⃣ Sorting Strings ⭐

Output

📌 Default sorting is lexicographical (ASCII-based)

Case-Insensitive Sort ⭐⭐

4️⃣ Sorting with Custom Logic (Closures) ⭐⭐

Output

5️⃣ Sorting Custom Objects ⭐⭐⭐ (Interview Favorite)

Example Model

Sort by Marks (Ascending)

Sort by Name (Descending)

6️⃣ Multiple-Criteria Sorting ⭐⭐⭐

📌 Sort by marks first, then name

7️⃣ Sorting Dictionaries ⭐⭐⭐

Dictionaries are unordered, so you must convert them first.

Output

📌 Result type: [(key: String, value: Int)]

8️⃣ Stable Sorting (Important Concept) ⭐⭐

Swift’s sort is not guaranteed stable.

✔ Stable alternative:

📌 Preserves original order for equal keys

9️⃣ Sorting with Comparable ⭐⭐⭐

Conform to Comparable

Use Direct Sorting

🔟 Performance & Best Practices ⭐⭐⭐

1️⃣1️⃣ Common Mistakes ❌

❌ Using sorted() when mutation needed
❌ Forgetting dictionaries are unordered
❌ Complex closure hurting readability
❌ Sorting inside loops

📌 Interview Questions (Swift Sorting)

Q1. Difference between sort() and sorted()?
👉 In-place vs new array

Q2. Are Swift sorts stable?
👉 Not guaranteed

Q3. How to sort custom objects?
👉 Closures or Comparable

Q4. How to sort dictionary?
👉 Convert to array first

✅ Summary

✔ sorted() → returns new array
✔ sort() → modifies array
✔ Closures enable custom logic
✔ Custom types use Comparable
✔ Dictionaries require conversion
✔ Stable sorting needs extra logic
✔ Very important for Swift interviews