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I want to avoid global variables when using my own classes in Arduino. Here is a example.
void setup(){
/* setup here */
classA objectA;
}
void loop(){
objectA.someMethod();
}
I know that my compiler will complain about it (out of scope, etc) but is it possible to do that or just forget it and use globally?
Thanks in advance!
If you want a variable to be available within more than one function it has to be global. There is no other possible way of doing it.
If you are only using the variable in the loop() function and nowhere else you can declare it static in loop(), which has the same effect of making it global, but it is only possible to see it within loop().
You can make a pointer global, then create a new object in setup() (using new...) and assign it to the pointer, but that has the potential of making a mess of your heap and should be avoided unless absolutely necessary. Also it's pointless, because you don't gain anything over having the object statically created in the global scope.
setup() function and just treat loop() like main(). Stick a while(1) at the end of loop() to stop it looping, define all your variables as local to loop(), then pass them all as parameters to where they are going. What do you end up with? You end up with global now inside loop() and allocated on the stack instead of the BSS. Big deal. Just stick with global, it's easier.
MyClass foo;) you are reserving the RAM at compilation time. All other ways of doing it involve dynamic RAM allocation and that is bad on a microcontroller.