Passing a class to a class

Community General Discussion
1

I have a mainline sketch that is using the following library, class, and function (simplified version):

#include <TFT_eSPI.h>
:
TFT_eSPI showPanel = TFT_eSPI();
TFT_eSprite sprite = TFT_eSprite(&showPanel);
:
void somefunction() {
:
uint16_t colour = 0;
sprite.drawPixel(x, y, colour);
:
};

and I am trying to write my own class in which I would like to do the sprite.drawPixel function. In other words I would like to do the sprite.drawPixel function from within the class rather than within the main sketch.

My problem is trying to find a way to pass sprite into the class that I am writing.

I have done a bunch of searching/reading over the last couple days but am getting no where.

Ideally, I believe I would pass a pointer to sprite into my class, and then reference it somehow within class to perform the
sprite.drawPixel(x, y, colour);

However, I am totally stuck on how to define the public and private portions of the class such that I can pass the sprite in from the calling mainline sketch, as well as how to define the call in the sketch.

I hope the above is clear, and that someone can share a concreate example of how to do this correctly.

With thanks

2

If the sprite is also used outside of the class, this would be an option. Otherwise you could consider making sprite a member variable.

3

If you are using setting up an instance of sprite outside of a class then taking your example, you could possibly do something like this:

MyClass.h:

#ifndef MyClass_h
#define MyClass_h

#include <Arduino.h>
#include <TFT_eSPI.h>

class MyClass {
public:
	MyClass();
	void someFunction(TFT_eSprite &sprite);
private:
};

#endif	// MyClass.h

MyClass.cpp:

#include MyClass.h

MyClass::MyClass(){
  :
}

MyClass::someFunction(TFT_eSprite &sprite){
  :
  uint16_t colour = 0;
  sprite.drawPixel(x, y, colour);
  :
}

Main .ino:

#include <TFT_eSPI.h>
#include "MyClass"

TFT_eSPI showPanel = TFT_eSPI();
TFT_eSprite sprite = TFT_eSprite(&showPanel);

MyClass myClassInstance;

void loop {
  :
  myClassInstance.someFunction{sprite};
  :
}

This is passing by reference. The sprite object could also be passed by pointer, or as stated, included and instantiated within the class.

1 Like
4

Thank you - this looks super helpful. I've started to implement it and its looking pretty promising at this point. Very thoughtful of you to have posted such a thorough reply. I'm sure it will be of help to others too. Thanks again.

Edit: @bitseeker I finalized building this - the above worked great - thanks again!

5

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