What Does a Go Type Declaration Like `type PublicKey []byte` Actually Do?

Understanding Type Declarations in Go

In Go, a common question arises regarding declarations like the following:

type PublicKey []byte

This type declaration establishes a new type named PublicKey. However, it's essential to understand what this declaration implies.

Type Definition

Contrary to popular belief, this declaration is not about creating a struct that inherits from []byte. Instead, it's a type definition that creates a new type with []byte as its underlying type.

Underlying Type and Operations

With this type definition, PublicKey is treated as a distinct type, sharing the same underlying type and operations as []byte. This means that any operations applicable to []byte, such as indexing, slicing, and appending, can also be performed on PublicKey.

Identity and Methods

Unlike inheritance in some other languages, type definitions in Go do not involve inheritance. PublicKey is independent of its underlying type, and it has no built-in methods. However, new methods can be attached to the PublicKey type in the future if needed.

Purpose of Type Definitions

Type definitions are primarily used to provide a consistent and descriptive name to a specific type. This makes it easier to work with types that are used multiple times throughout the codebase or to express concepts more clearly.

Comparison to Functions

While one may think of using functions to perform similar tasks, type definitions offer key advantages. They enable the implementation of interfaces, which is impossible with functions. Interfaces define specific methods that types must implement, ensuring compatibility and extensibility.

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