Exported vs. unexported fields (private vs public)

Struct fields whose names begin with an uppercase letter are exported. All other names are unexported.

type Account struct {
    UserID      int    // exported
    accessToken string // unexported
}

Unexported fields can only be accessed by code within the same package. As such, if you are ever accessing a field from a different package, its name needs to start with an uppercase letter.

package main

import "bank"

func main() {
    var x = &bank.Account{
        UserID: 1,          // this works fine
        accessToken: "one", // this does not work, since accessToken is unexported
    }
}

However, from within the bank package, you can access both UserId and accessToken without issue.

The package bank could be implemented like this:

package bank

type Account struct {
	UserID int
  accessToken string
}

func ProcessUser(u *Account) {
	// ProcessUser() can access u.accessToken because
	// it's defined in the same package
  u.accessToken = doSomething(u) 
}

Found a mistake? Have a question or improvement idea? Let me know.

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