Challenge: Composite Pattern

In this challenge, you have to implement the composite pattern to solve the given problem.

We'll cover the following

Problem statement

In this challenge, you have to implement a directory system using the composite pattern.

You have been given the following skeleton code:

class Directory{
    constructor(name,lastModified,size){
        this.name = name
        this.lastModified = lastModified
        this.size = size
    }
    getLastmodified(){}
    getSize(){}
    getName(){}
}
class File extends Directory{
}
class Folder extends Directory{
}

It’s up to you to figure out which class will be the component, leaf subclass, and composite subclass.

A Directory has the following properties:

  • name: name of the file/folder.

  • lastModified: time in minutes since the last modification.

  • size: the size of the file/folder in kilobytes.

You have the following functions in the Directory class:

  • getLastmodified: Returns the lastModified time of a file. In the case of a folder with multiple files, it should return the minimum of the lastmodified times of all files.

  • getSize: Returns the size of a file/folder.

  • getName: Returns the name of the file or all the files in the case of a folder.

The composite subclass should contain the following additional functions as well:

  • addFile

  • removeFile

Input

Calling the given functions on files and folders

Output

The correct output after calling these functions such as lastModified time, name and size

Sample input

const file = new File("penguiny.png",6,12)
file.getLastmodified()
file.getName()
file.getSize()

Sample output

6
"penguiny.png"
12

Challenge #

Take a close look and design a step-by-step solution before jumping on to the implementation. This problem is designed for your practice, so try to solve it on your own first. If you get stuck, you can always refer to the solution provided. Good Luck!

//Component
class Directory{
    constructor(name,lastModified,size){
        this.name = name
        this.lastModified = lastModified
        this.size = size
    }
    getLastmodified(){}
    getSize(){}
    getName(){}
}
//Leaf subclass
class File extends Directory{
}
//Compsoite subclass
class Folder extends Directory{
}

Let’s discuss the solution in the next lesson.