error: use of 'this' in a constant expression in Arduino Class - c++

Question

i am trying to write a class for an arduino projekt, i am using the information in http://paulmurraycbr.github.io/ArduinoTheOOWay.html as a guide.
I want to set up a lighstrip for further use and constantly keep getting the errormessage: error: use of 'this' in a constant expression.
My code looks like this:
#include <FastLED.h>
#define LED_STRIP_PIN 2
#define LED_STRIP_NUM_LEDS 10
//const unsigned char LED_STRIP_PIN = 2;
//const int LED_STRIP_NUM_LEDS = 10;
CRGB leds[LED_STRIP_NUM_LEDS];
class LedStrip {
unsigned char pin;
public:
LedStrip(unsigned char attachTo) :
pin(attachTo)
{
};
void setup() {
FastLED.addLeds<NEOPIXEL, pin>(leds, 10);
};
};
//LedStrip ledstrip(LED_STRIP_PIN, LED_STRIP_NUM_LEDS);
LedStrip ledstrip(LED_STRIP_PIN);
void setup() {
}
void loop() {
}
I have tried reading up on what might cause this error, but frankly i do not understand any of it. As far as i have understood it seems like i cannot use a const there (which i am not, i think) since it might be modified during code execution.
the complete error looks like thissketch_feb03b.ino: In member function 'void LedStrip::setup()':
sketch_feb03b:20:33: error: use of 'this' in a constant expression
FastLED.addLeds<NEOPIXEL, pin>(leds, 10);
^~~

Answer 1

Your issue is that pin is not a compile-time constant, and all template arguments must be compile-time constants.
There might be other options, but the (probably) easiest one is passing pin as template argument itself:
template<int pin> // make sure type of pin is correct, I don't know what addLeds expect
class LedStrip {
public:
LedStrip() //not really needed now
{
};
void setup() {
FastLED.addLeds<NEOPIXEL, pin>(leds, 10);
};
};
Usage:
//if LED_STRIP_PIN is a compile-time constant, i.e. a macro or a const(expr) value
LedStrip<LED_STRIP_PIN> ledstrip;
//if LED_STRIP_PIN is obtained at runtime, you cannot it use it at all.
LedStrip<7> ledstrip;

Answer 2

#include <FastLED.h>
const int NUM_LEDS01 = 49; //Missing one LED from string of 50 LEDS
const int DATA_PIN01 = 2; //White wire to GND, Red wire to 5V, Black Wire is data.
CRGB leds01[NUM_LEDS01]; //First strng of LEDS
const int NUM_LEDS02 = 50;
const int DATA_PIN02 = 3; //White wire to GND, Red wire to 5V, Black Wire is data.
CRGB leds02[NUM_LEDS02]; //Second String of LEDS
//#include "Lstring.h"
template<int dataPin>
class Lstring{
private:
int nleds = 0; //initialise to some number
CRGB *ledS;
public:
Lstring(){}
Lstring(CRGB *lds, int nleds){
this->nleds = nleds;
ledS = lds;
}
void ledOn(int ledNum){
ledS[ledNum] = CRGB::Blue;
FastLED.show();
}
void ledOff(int ledNum){
ledS[ledNum] = CRGB::Black;
FastLED.show();
}
void initialise(){
FastLED.addLeds<WS2811,dataPin>(ledS,nleds);
}
};
//---------------------------------
Lstring<DATA_PIN01> lstring01(leds01, NUM_LEDS01);
Lstring<DATA_PIN02> lstring02(leds02, NUM_LEDS02);
void setup() {
lstring01.initialise();
lstring02.initialise();
}
void loop() {
lstring01.ledOn(8);
delay(200);
lstring01.ledOff(8);
delay(200);
lstring02.ledOn(8);
delay(200);
lstring02.ledOff(8);
delay(200);
}