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GO Structures

Table of Contents

Installation

To install the project, run:

git clone https://github.com/Githaiga22/GO-Structures.git

Introduction

  • What is a Struct?

    • In Go, a struct is a collection of fields or variables, which can be of different types, that are grouped together to represent a more complex entity.
    • Think of a struct as a blueprint or template used to create a more complex data structure like a Person, Car, or Book.

  • Why Use Structs?

    • To organise and bundle related data together.
    • They allow you to model real-world things like a customer or product, each having multiple attributes (fields).

Declaring a Struct

Syntax:

type StructName struct {
field1 DataType
field2 DataType
...
}

Example 1: A simple Person struct

type Person struct { 
Name string
 Age int
 Gender string 
}

This example defines a Person struct with three fields: Name (string), Age (int), and Gender (string).

Creating and Initializing a Struct

Method 1: Using the Field Names

  • You can create an instance of a struct by explicitly specifying the field names and values.

Example:

person := Person{
	Name:   "John Doe",
	Age:	25,
	Gender: "Male",
}

testing

package main

import "fmt"

type Person struct {
	name string
	age int
	gender string
}

func main() {
	person := Person{
		name : "Allan kamau",
		age : 23,
		gender : "male",

	}
fmt.Println("Name:", person.name)
fmt.Println("age:", person.age)
fmt.Println("gender:", person.gender)
}

//output
Name: Allan kamau
age: 23
gender: male

Accessing Struct Fields

Once a struct is created, you can access its fields using the dot (.) operator.

Example:

fmt.Println("Name:", person.name)
fmt.Println("age:", person.age)
fmt.Println("gender:", person.gender)

Modifying Struct Fields

  • You can also modify the fields of a struct after it has been created.

Example 1:

package main

import "fmt"

type Person struct {
 name string
 age int
 gender string
}

func main() {
 person := Person{
 	name : "Allan kamau",
 	age : 23,
 	gender : "male",

 }
fmt.Println("Name:", person.name)
fmt.Println("age:", person.age)
fmt.Println("gender:", person.gender)

person.age = 26
//modifying agefields
fmt.Println("updated Age:", person.age)

//output
Name: Allan kamau
age: 23
gender: male
updated Age: 26
}

Struct Methods

Go allows you to define methods on structs, just like functions, but these methods are tied to a struct and can access its fields.

Example 2:

Adding a Method to Person

package main

import "fmt"

type Person struct {
   name string
   age int
   gender string
}
//define method greet on person struct
func (p Person) Greet() string {
   return "Hello, my name is " + p.name
}
func main() {
   person := Person{
   	name : "Allan kamau",
   	age : 23,
   	gender : "male",

   }
fmt.Println(person.Greet())

//output
Hello, my name is Allan kamau
}

Struct with Nested Structs

Sometimes, structs can contain other structs as fields, allowing for more complex data modeling.

Example 3:

A Student struct containing an Address struct

package main

import "fmt"

type Address struct {
	city string
	state string
}
type Student struct {
	Name string
	Age int
	Address Address
}
func main() {
	student := Student{
		Name: "Fred Gitonga",
		Age: 21,
		Address: Address{
			city: "Kisumu",
			state: "Mamboleo",
		},
	}
fmt.Println(student.Name, "lives in", student.Address.city)
}

//ouput
fred gitonga lives in kisumu

Structs with Functions as Fields

You can even add functions to a struct as fields, allowing for flexible behaviors inside your structs.

Example 4:

Calculator struct with function fields

package main

import "fmt"


type Calculator struct {
   Add func(a, b int)  int
}

func main() {
   calculator  := Calculator{
   	Add: func(a, b int) int {
   		return a + b
   	},
   }
result := calculator.Add(3, 5)
fmt.Println("Sum:", result)
}

//output
Sum: 8

Pointers to Structs

In Go, structs can be passed by value or by reference (using pointers). Passing by reference allows you to modify the original struct.

Example 5:

Passing a Pointer to a Struct

package main 

import "fmt"

type Person struct {
	Name string
	Age int
	gender string
}

func UpdateAge(p *Person, newAge int) {
	p.Age = newAge
}
func main() {
	john := Person{ Name: "john", Age: 25, gender: "Male"}
	UpdateAge(&john, 26)
	fmt.Println(john.Age) 

}

//output
26

Common Mistakes with Structs

  • Uninitialized Fields: If you don't initialize a field, Go automatically assigns a zero value (empty string, 0, false, etc.).
  • Using pointers when not needed: For small structs, passing by value may be more efficient.

Practice Problems

  • Easy: Create a Book struct with fields Title, Author, and Pages. Write a method to display the book's info.
  • Intermediate: Create a Library struct that holds multiple Book structs. Write methods to add a book and list all books in the library.
  • Hard: Create a Vehicle struct with fields like Make, Model, and Year. Then create a Fleet struct that manages multiple vehicles, including adding, removing, and searching vehicles by year.

Conclusion

Key Points to Remember:

  • Structs are used to group related data.
  • Use methods to add functionality to structs.
  • Pointers allow you to modify structs in place.
  • Structs can be nested or contain functions as fields.

Author

Allan Githaiga Kamau

Github profile

Githaiga22