Raw values for enums in Swift - Time & Space Complexity

Time Complexity: Raw values for enums

O(n)

Understanding Time Complexity

Let's see how the time it takes to work with enums that have raw values changes as we use more cases.

We want to know how the program's steps grow when looking up enum values by their raw values.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

enum Direction: String {
    case north = "N"
    case south = "S"
    case east = "E"
    case west = "W"
}

let input = "E"
if let direction = Direction(rawValue: input) {
    print("Found direction: \(direction)")
}
    

This code tries to find an enum case from a raw string value.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Checking each enum case's raw value to find a match.
• How many times: Up to once for each enum case until a match is found.

How Execution Grows With Input

As the number of enum cases grows, the program may check more cases to find a match.

Input Size (number of enum cases)	Approx. Operations (checks)
4	Up to 4 checks
10	Up to 10 checks
100	Up to 100 checks

Pattern observation: The number of checks grows directly with the number of enum cases.

Final Time Complexity

Time Complexity: O(n)

This means the time to find a matching raw value grows linearly with the number of enum cases.

Common Mistake

[X] Wrong: "Looking up an enum by raw value is instant no matter how many cases there are."

[OK] Correct: The program may need to check each case one by one until it finds a match, so more cases mean more checks.

Interview Connect

Understanding how enum raw value lookups scale helps you explain how your code behaves with more data, a useful skill in real projects and interviews.

Self-Check

"What if the enum used integers as raw values instead of strings? How would the time complexity change?"

Practice

1. What is the purpose of raw values in Swift enums?

easy

A. To allow enums to inherit from classes

B. To assign fixed simple values like strings or numbers to enum cases

C. To make enums mutable after declaration

D. To create functions inside enums

Solution

1. Step 1: Understand what raw values are

   Raw values are fixed values assigned to enum cases, like strings or numbers.

2. Step 2: Identify the purpose of raw values

   They help convert enum cases to simple data types for saving or displaying.

3. Final Answer:

   To assign fixed simple values like strings or numbers to enum cases -> Option B

4. Quick Check:

   Raw values = fixed simple values [OK]

Hint: Raw values give enums fixed simple data like strings or numbers [OK]

Common Mistakes:

• Thinking raw values make enums mutable
• Confusing raw values with associated values
• Believing enums can inherit from classes

2. Which of the following is the correct syntax to declare an enum with raw values in Swift?

easy

A. enum Direction: Int { case north; case south }

B. enum Direction { case north = "N" case south = "S" }

C. enum Direction: String { case north = "N" case south = "S" }

D. enum Direction: String { north = "N", south = "S" }

Solution

1. Step 1: Check enum declaration with raw values

   Raw values require specifying the type after enum name, e.g., : String.

2. Step 2: Verify correct case syntax

   Cases use 'case name = value' syntax, separated by new lines or semicolons.

3. Final Answer:

   enum Direction: String { case north = "N" case south = "S" } -> Option C

4. Quick Check:

   Raw value enum syntax = enum Direction: String { case north = "N" case south = "S" } [OK]

Hint: Raw value enums need type after name and '=' for values [OK]

Common Mistakes:

• Omitting the raw value type after enum name
• Using commas instead of separate case lines
• Assigning raw values without specifying type

3. What will be the output of this Swift code?

enum Weekday: Int {
    case monday = 1
    case tuesday
    case wednesday
}
print(Weekday.tuesday.rawValue)

medium

A. 1

B. Error: rawValue not found

C. 3

D. 2

Solution

1. Step 1: Understand raw value auto-increment

   When the first case has a raw value (1), following cases auto-increment by 1.

2. Step 2: Identify raw value of 'tuesday'

   Since monday = 1, tuesday = 2, wednesday = 3.

3. Final Answer:

   2 -> Option D

4. Quick Check:

   Auto-increment raw values = 2 [OK]

Hint: Raw Int values auto-increment from first assigned value [OK]

Common Mistakes:

• Assuming all raw values must be explicitly assigned
• Confusing rawValue with case index
• Expecting an error when accessing rawValue

4. Identify the error in this enum declaration:

enum Color: String {
    case red = 1
    case green = "Green"
    case blue = "Blue"
}

medium

A. Raw values must all be of the declared type String

B. Enum cases cannot have raw values

C. Raw values must be integers only

D. Missing semicolon after each case

Solution

1. Step 1: Check raw value type consistency

   The enum declares raw type String, so all raw values must be strings.

2. Step 2: Identify the incorrect raw value

   Case 'red' has raw value 1 (an Int), which conflicts with String type.

3. Final Answer:

   Raw values must all be of the declared type String -> Option A

4. Quick Check:

   Raw values must match enum type [OK]

Hint: All raw values must match enum's declared raw type [OK]

Common Mistakes:

• Mixing raw value types in one enum
• Thinking semicolons are required after cases
• Believing enums can't have raw values

5. Given this enum:

enum StatusCode: Int {
    case success = 200
    case notFound = 404
    case serverError = 500
}

func message(for code: Int) -> String {
    if let status = StatusCode(rawValue: code) {
        switch status {
        case .success: return "OK"
        case .notFound: return "Not Found"
        case .serverError: return "Server Error"
        }
    } else {
        return "Unknown"
    }
}

print(message(for: 404))
print(message(for: 201))

What is the output?

hard

A. Not Found
Unknown

B. OK
Unknown

C. Not Found
Server Error

D. Error at runtime

Solution

1. Step 1: Understand rawValue initializer

   StatusCode(rawValue: 404) returns .notFound; 201 returns nil.

2. Step 2: Trace function output for each input

   For 404, returns "Not Found"; for 201, returns "Unknown".

3. Final Answer:

   Not Found Unknown -> Option A

4. Quick Check:

   Raw value init maps code to enum or nil [OK]

Hint: Raw value init returns nil if no matching case [OK]

Common Mistakes:

• Assuming rawValue init always returns a case
• Confusing rawValue with case index
• Expecting runtime error for unknown raw value