Identifiable & Hashable

In Swift, Identifiable and Hashable are protocols that help define and work with types in different contexts, primarily related to collections and data structures.

Identifiable:

• Purpose:

  • The Identifiable protocol is designed for types whose instances have a stable identity.

• Requirement:

  • Requires the type to provide a property named id that uniquely identifies each instance.

• Usage:

  • Primarily used in conjunction with SwiftUI and SwiftUI-based frameworks, allowing for easier identification of items in lists and collections.

• Example:

  struct Item: Identifiable {
      let id: UUID
      let name: String
  }

  In this example, the Item struct conforms to Identifiable by providing a property named id. The usage of Identifiable is especially beneficial when working with SwiftUI’s List or ForEach views.

Hashable:

• Purpose:

  • The Hashable protocol is designed for types whose instances can be hashed into an integer value.

• Requirement:

  • Requires the type to implement the hash(into:) method to provide a consistent hash value for instances.

• Usage:

  • Essential for using instances of a type as keys in dictionaries or when working with sets.

• Example:

  struct Point: Hashable {
      let x: Int
      let y: Int
   
      func hash(into hasher: inout Hasher) {
          hasher.combine(x)
          hasher.combine(y)
      }
  }

  In this example, the Point struct conforms to Hashable by implementing the hash(into:) method. The method combines the hash values of its properties (x and y) into the hasher.

Combined Usage:

You might often see types that conform to both Identifiable and Hashable. This is common when working with collections where you want both stable identity and the ability to efficiently use instances as keys in dictionaries or elements in sets.

struct User: Identifiable, Hashable {
    let id: Int
    let username: String
}

In this case, instances of the User struct have both a stable identity through the id property and are hashable, making them suitable for use in collections like dictionaries or sets.

In summary, Identifiable and Hashable are protocols in Swift that serve different purposes but are often used together to provide a comprehensive way to identify and manage instances in collections or SwiftUI views.