https://github.com/jjv360/nim-classes

Adds class support to Nim.
https://github.com/jjv360/nim-classes

Last synced: 2 months ago
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Adds class support to Nim.

• Host: GitHub
• URL: https://github.com/jjv360/nim-classes
• Owner: jjv360
• License: mit
• Created: 2020-10-24T00:53:08.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2023-03-13T14:44:05.000Z (almost 2 years ago)
• Last Synced: 2024-08-04T03:05:00.730Z (6 months ago)
• Language: Nim
• Homepage:
• Size: 56.6 KB
• Stars: 89
• Watchers: 7
• Forks: 3
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-nim - classes - Python-style class system for Nim. (Language Features / Object-Oriented Programming)

README

        
# Classes

![](https://img.shields.io/badge/status-beta-orange)

A collection of macros which add class support to Nim. To install, run `nimble install classes`. Features include:

- Simple class syntax

- Class variables with default values

- Inheritance and `super.calls()`

- Default constructors

- Static and abstract methods

- Methods and variables defined in any order

- Mixins

## Examples

```nim

import classes

# A base class

class Shape:

    ## The position of the shape

    var x = 0

    var y = 0

    ## Optional constructor

    method init() =

        echo "Creating a Shape"

    ## Optional destructor (not supported in JS)

    method deinit() =

        echo "Destroying a Shape"

    ## Abstract draw function

    method draw()

    ## Calculate size

    method calculateSize(): float = return 0

    ## Static method

    method defaultSize(): float {.static.} = 5

# A subclass

class Square of Shape:

    # Radius

    var radius = 5

    ## Override constructor

    method init() =

        super.init()

        echo "Creating a Square"

    ## Draw it

    method draw() =

        echo "Drawing a square of size " & $this.calculateSize()

    ## Calculate size

    method calculateSize(): float = super.calculateSize() + this.radius

# Many ways of creating class instances:

let obj = Square.init()

let obj = Square().init()

let obj = newSquare()

# Call static methods

# NOTE: Static methods don't always work if the name of your nim file is the exact same as the class name. 

# You may get a `type mismatch: got <>` error in that case.

Shape.defaultSize()

# Data only classes

class DataOnly:

    var v0 = 7

    var v1: int

    var v2: string

# Constructing it this way allows you to pass in values for the variables that don't have values set

let obj = DataOnly(v1: 10, v2: "20").init()

# Using the mixin keyword will copy the variables and methods from one class to another

class CustomNote:

    var note = ""

class Circle of Shape:

    mixin CustomNote

let circle = Circle.init()

circle.note = "My custom note"

# Singleton classes act the same way as standard classes, but use a .shared() accessor instead of constructors.

# The default constructor is called the first time the singleton class is accessed.

singleton MySingletonClass:

    var v1 = 7

    method init() = echo "Singleton accessed for the first time!"

# Access the singleton, this also triggers the init() the first time

echo MySingletonClass.shared.v1

```

## Issues

- **JS backend:** As of Nim 1.4.8 (when I last tested), the internal [dom](https://nim-lang.org/docs/dom.html#class%2CNode) library is exposing a `class()` function, and this function always takes precedent over this library's `class` macro. I don't know how to fix this. In the mean time, you can replace the word `class` with `classes.class`