Struct Manipulation in Go

Introduction

This lab aims to test your knowledge of Go's structs, which are typed collections of fields. Structs are useful for grouping data together to form records.

Structs

In this lab, you need to complete the newPerson function that constructs a new person struct with the given name. The person struct type has name and age fields.

• The person struct type must have name and age fields.
• The newPerson function must construct a new person struct with the given name.
• The newPerson function must return a pointer to the newly created person struct.
• The main function must print the following:
  • A new struct with name "Bob" and age 20.
  • A new struct with name "Alice" and age 30.
  • A new struct with name "Fred" and age 0.
  • A pointer to a new struct with name "Ann" and age 40.
  • A new struct constructed using the newPerson function with name "Jon" and age 42.
  • The name field of a struct with name "Sean" and age 50.
  • The age field of a struct pointer to a struct with name "Sean" and age 50.
  • The age field of a struct pointer to a struct with name "Sean" and age 50 after the age field has been updated to 51.

$ go run structs.go
{Bob 20}
{Alice 30}
{Fred 0}
&{Ann 40}
&{Jon 42}
Sean
50
51

There is the full code below:

// Go's _structs_ are typed collections of fields.
// They're useful for grouping data together to form
// records.

package main

import "fmt"

// This `person` struct type has `name` and `age` fields.
type person struct {
    name string
    age  int
}

// `newPerson` constructs a new person struct with the given name.
func newPerson(name string) *person {
    // You can safely return a pointer to local variable
    // as a local variable will survive the scope of the function.
    p := person{name: name}
    p.age = 42
    return &p
}

func main() {

    // This syntax creates a new struct.
    fmt.Println(person{"Bob", 20})

    // You can name the fields when initializing a struct.
    fmt.Println(person{name: "Alice", age: 30})

    // Omitted fields will be zero-valued.
    fmt.Println(person{name: "Fred"})

    // An `&` prefix yields a pointer to the struct.
    fmt.Println(&person{name: "Ann", age: 40})

    // It's idiomatic to encapsulate new struct creation in constructor functions
    fmt.Println(newPerson("Jon"))

    // Access struct fields with a dot.
    s := person{name: "Sean", age: 50}
    fmt.Println(s.name)

    // You can also use dots with struct pointers - the
    // pointers are automatically dereferenced.
    sp := &s
    fmt.Println(sp.age)

    // Structs are mutable.
    sp.age = 51
    fmt.Println(sp.age)
}

Summary

In this lab, you learned how to use Go's structs to group data together to form records. You also learned how to create new structs, access struct fields, and update struct fields.