Private Class Data

When to Use (Problem)

• When the problem requires a unification for private class data across different classes definitions.
• When the problem requires special encapsulation, where it wants to maximize its encapsulation capabilities by greatly minimizing the visibility of attributes accessibility.

Example (Solution)

Here is an example in Go:

package main

import (

        "fmt"

)

type privateClass struct {

        sharedData string

}

type PublicClass1 struct {

        ID   uint

        data *privateClass

}

func (p *PublicClass1) Init() {

        p.data = &privateClass{}

}

func (p *PublicClass1) SaveData(data string) {

        p.data.sharedData = data

}

func (p *PublicClass1) ReadData() string {

        return p.data.sharedData

}

func main() {

        p := PublicClass1{}

        p.Init()

        p.SaveData("core1")

        p.ID = 5

        fmt.Printf("Access to id: %v\n", p.ID)

        fmt.Printf("Get data: %v\n", p.ReadData())

}

// Output:

// Access to id: 5

// Get data: core1

Notice that the client is not able to access the private class's sharedData directly. Only the PublicClass1 is able to access the private class data. If we use singleton creational design pattern for the private class, we can unify all private data for all public classes.

Expected Outcome (Consequences)

• Private data is unified under a single private class.
• All classes using the private data class shares the same shared data if singleton design pattern is used.
• Client is not able to directly access private data but limited to the public versions.