const char*, extern const char*, My Custom Library

Projects Programming
4

I think, I did not explain my problem well. Here are contents of sketch, header and .cpp file.

Sketch:

#define CLIENT_ID "MY_ID"

Header:

#define IDS 0

#ifndef CLIENT_ID 
#define IDS 1
#endif

.cpp

if(IDS == 1)
	{
		Serial.println("client id is not define");
		_CLIENT_ID = String(ESP.getChipId());
		Serial.println(CLIENT_ID);
		Serial.println(_CLIENT_ID);
	}
	else
	{
		_CLIENT_ID = CLIENT_ID;
		Serial.println("client id is already define");
		Serial.println(CLIENT_ID);
		Serial.println(_CLIENT_ID);
	}

_CLIENT_ID is a String variable which is defined in header class private: section.

Error:
error: 'CLIENT_ID' was not declared in this scope _CLIENT_ID = CLIENT_ID;