Library initialisation and loop wrapped in compiler directives: Error

Using Arduino Programming Questions
#1

Hi,

I get a weird error with program that has got a library initialisation and loop wrapped in compiler directives.
Here is my code (simplified to the minimum) to get the error:

//========= (Hardware definitions) =========
//Set definitions to 1 when hardware is present:
#define RF24L01 false
#define LoRaSPI false
#define Display4Dig true
#define Nokia5110Display false
#define OLED128x64Display false
#define OLED64x48Display false

//4*7 Segment LED
#if Display4Dig
#include "TM1637Display.h"
#define CLK 6
#define DIO 5
#endif

void setup() {
  //Initialisation Display Hardware
#if Display4Dig
  TM1637Display display(CLK, DIO);
  display.setBrightness(0x08);
  //Turn off segments 1&2, write "dB" on 3&4.
  byte data[] = {0x0, 0x0, 0b01011110 , 0b01111100};
  display.setSegments(data);
#endif
}

void loop() {
  //==== (Display) ======
#if Display4Dig
  //TM1637Display display(CLK, DIO);
  //display.setBrightness(0x08);
  display.showNumberDec(int(23), false, 2, 0);
#endif

}

The library is initialised correctly and should run, but since they are wrapped in compiler directives I got the error:
exit status 1
'display' was not declared in this scope
on instruction
display.showNumberDec(int(23), false, 2, 0);

The complete programm has many such options which were previously all compiled and conditionally executed.
I wanted to redesign the code to be more compact and fit into an ATmega168.
I failed with replacing the conditions with compiler directives.

How can I get it the right way?

For your info:
The program compiles correctly
-if the library is unconditionally included or
-if I uncomment the //TM1637Display display(CLK, DIO); line which repeats the initialization i the loop.
But that's IMHO not the way it should be.

Thank you for your advice.
Laszlo

#2

This line:

  TM1637Display display(CLK, DIO);

creates a TM1637Display object that is local to the setup function. Because it’s local, you can’t use it in the loop function. The solution to be able to use it in both the setup and loop functions is to make the display object global by moving it outside the setup function.

More information:
https://www.arduino.cc/reference/en/language/variables/variable-scope--qualifiers/scope/

#3

pert:
The solution to be able to use it in both the setup and loop functions is to make the display object global by moving it outside the setup function.

[patting myself on the forehead]

Thank you, I had moved inadvertently that instruction in the init() section.
Sometimes the solution is just more obvious to other eyes!

Merry Chrismas and Season greetings.

#4

You're welcome. I'm glad if I was able to be of assistance. Enjoy!
Per

#5