Generic subscripts in Swift - Mini Project: Build & Apply

Using Generic Subscripts in Swift

📖 Scenario: Imagine you have a collection that stores different types of values, like numbers and words. You want to access these values easily using a special way called a generic subscript.

🎯 Goal: Build a Swift struct called MultiTypeStorage that uses a generic subscript to get and set values of different types by their keys.

📋 What You'll Learn

Create a struct called MultiTypeStorage with a dictionary property named storage of type [String: Any].

Add a generic subscript subscript(key: String) -> T? to get and set values of any type T.

Use the generic subscript to store and retrieve values of different types by their keys.

Print the retrieved values to show the generic subscript works.

💡 Why This Matters

🌍 Real World

Generic subscripts help manage collections that store mixed types, like user settings or configuration data, making code cleaner and safer.

💼 Career

Understanding generic subscripts is useful for Swift developers working on flexible data storage, APIs, or frameworks that handle various data types.

1

Create the MultiTypeStorage struct with a storage dictionary

Create a struct called MultiTypeStorage with a variable storage of type [String: Any] initialized as an empty dictionary.

Swift

struct MultiTypeStorage {
    // Your code here
}

Need a hint?

Use struct MultiTypeStorage { var storage: [String: Any] = [:] } to create the struct and dictionary.

2

Add a generic subscript to MultiTypeStorage

Inside MultiTypeStorage, add a generic subscript subscript(key: String) -> T? that gets and sets values in storage. For getting, cast the stored value to T. For setting, assign the new value to storage[key].

Swift

struct MultiTypeStorage {
    var storage: [String: Any] = [:]

    // Your code here
}

Need a hint?

Use subscript(key: String) -> T? with get and set blocks to access storage.

3

Store values of different types using the generic subscript

Create a variable storage of type MultiTypeStorage. Use the generic subscript to set storage["age"] = 30 and storage["name"] = "Alice".

Swift

struct MultiTypeStorage {
    var storage: [String: Any] = [:]

    subscript(key: String) -> T? {
        get {
            return storage[key] as? T
        }
        set {
            storage[key] = newValue
        }
    }
}

// Your code here

Need a hint?

Create var storage = MultiTypeStorage() and assign values using storage["age"] = 30.

4

Retrieve and print values using the generic subscript

Use the generic subscript to get age as Int? and name as String? from storage. Print both values using print(age) and print(name).

Swift

struct MultiTypeStorage {
    var storage: [String: Any] = [:]

    subscript(key: String) -> T? {
        get {
            return storage[key] as? T
        }
        set {
            storage[key] = newValue
        }
    }
}

var storage = MultiTypeStorage()
storage["age"] = 30
storage["name"] = "Alice"

// Your code here

Need a hint?

Retrieve values with let age: Int? = storage["age"] and print them.