Builder Design Pattern Using Golang

What is Builder Design Pattern ?

• It is a creational design pattern that allows you to create step by step & lets you choose only the parts you need.

Why do we need it ?

• Imagine creating a game character:

warrior := Character{
    Name:"Avenger",
    Health:100,
    Attack:20,
    Defence:15,
    Weapon:"Sword",
    Armor:"Steel Armor",
    Skill:"Fire Strike",
}

• Now imagine the character has 20 fields, the constructor looks ugly.

Builder Solution

• Build the object step by step

warrior := NewCharacterBuilder()
        .SetName("Avenger")
        .SetHealth(100)
        .SetAttack(20)
        .SetWeapon("Sword")
        .Build()

• Now this is more readable

Code:

type Character struct {
    Name string
    Attack int
    Health int
    Defence int
    Weapon string
    Armor string
    Skill string
}

type CharacterBuilder struct {
    char Character
}

• **Character is a struct (like a blueprint) that defines what a game character has (name, attack, health, weapon, etc.).**
• CharacterBuilder is another struct used to help build or create a Character step by step.
• It contains a char field, which stores the character being built inside the builder.

func NewCharacter()*CharacterBuilder{
    return &CharacterBuilder{}
}

• NewCharacter is a constructor function that creates a new CharacterBuilder.
• It returns a pointer to an empty builder object, ready to be used for building a character.

func(c *CharacterBuilder)SetName(val string)*CharacterBuilder{
    c.char.Name = val
    return c
}

func(c *CharacterBuilder)SetAttack(val int)*CharacterBuilder{
    c.char.Attack = val
    return c
}

func(c *CharacterBuilder)SetDefence(val int)*CharacterBuilder{
    c.char.Defence = val
    return c
}

func(c *CharacterBuilder)SetHealth(val int)*CharacterBuilder{
    c.char.Health = val
    return c
}

func(c *CharacterBuilder)SetWeapon(val string)*CharacterBuilder{
    c.char.Weapon = val
    return c
}

func(c *CharacterBuilder)SetArmor(val string)*CharacterBuilder{
    c.char.Armor = val
    return c
}

func(c *CharacterBuilder)SetSkill(val string)*CharacterBuilder{
    c.char.Skill = val
    return c
}

• These are builder methods that set different fields (Name, Attack, Health, etc.) of the Character.
• Each function updates one property inside the char object of CharacterBuilder.
• After setting the value, they return the builder (c) itself so you can chain multiple calls together.
• This pattern makes it easy to build a character step by step in a clean way.

func(c *CharacterBuilder)Build()Character {
    return c.char
}

• This Build() function returns the completed character from the builder.
• It is usually called at the end to get the final object after setting all values.

func main(){

    warrior := NewCharacter().SetName("Avenger").SetAttack(80).SetHealth(100).SetWeapon("Magic").Build()

    fmt.Println(warrior)

}

• In main, a character is created step-by-step using method chaining (setting name, attack, health, and weapon).
• Finally, Build() returns the complete character, and fmt.Println prints it.

Full Code :

package main

import (
    "fmt"
)

type Character struct {
    Name string
    Attack int
    Health int
    Defence int
    Weapon string
    Armor string
    Skill string
}

type CharacterBuilder struct {
    char Character
}

func NewCharacter()*CharacterBuilder{
    return &CharacterBuilder{}
}

func(c *CharacterBuilder)SetName(val string)*CharacterBuilder{
    c.char.Name = val
    return c
}

func(c *CharacterBuilder)SetAttack(val int)*CharacterBuilder{
    c.char.Attack = val
    return c
}

func(c *CharacterBuilder)SetDefence(val int)*CharacterBuilder{
    c.char.Defence = val
    return c
}

func(c *CharacterBuilder)SetHealth(val int)*CharacterBuilder{
    c.char.Health = val
    return c
}

func(c *CharacterBuilder)SetWeapon(val string)*CharacterBuilder{
    c.char.Weapon = val
    return c
}

func(c *CharacterBuilder)SetArmor(val string)*CharacterBuilder{
    c.char.Armor = val
    return c
}

func(c *CharacterBuilder)SetSkill(val string)*CharacterBuilder{
    c.char.Skill = val
    return c
}

func(c *CharacterBuilder)Build()Character {
    return c.char
}

func main(){

    warrior := NewCharacter().SetName("Avenger").SetAttack(80).SetHealth(100).SetWeapon("Magic").Build()

    fmt.Println(warrior)

}

Output:

{Avenger 80 100 0 Magic  }