No constructor for "only declaring" available about pcf8574_library

[xreef]

Hi alve89,
use void* pointer.
Bye Renzo

[alve89]

Thanks for your very quick reply!
I just tried a bit with this but still I don't see how to store the PCF8574 object as a property in a myClass object and "change" its address afterwards...? So my problem is the line PCF8574 myPCF; in my first post.

[xreef]

If you don't want to instantiate the object you have to use a pointer.
`
class myClass {
public:
PCF8574* getMyPCF();
void setMyPCF();

private:
PCF8574* myPCF;
};
`

But I think it's better if you declare first like in this example.

Bye Renzo

[alve89]

I understand that. The problem with only having the pointer is, that I would need to instantiate the object somewhere else (e.g. in global scope) but I don't want the user to instantiate it by himself, I want to provide an interface (get / set methods), so I thought of instantiating the object in the myClass object and use it with the getMyPCF() method.
The example you provided does exactly what I don't want: Declaring / defining the objects in global scope and use them in setup() (and loop()).

[alve89]

I just changed the library by the following things:

1. PCF8574.h: Adding default value for _address
2. PCF8574.h: Adding void setAddress(uint8_t address); and void setI2CPins(uint8_t sda, uint8_t scl);
3. PCF8574.cpp: Adding the definitions of the declarations above

If you find this helpful, feel free to use it. Beside this issue I think these changes can be helpful. If you see another way to solve this issue, I'm looking forward to your response!

PCF8574_library_emptyConstructor.zip

@xreef I just noticed an error in my code, I forgot the &Wire line - I added it and it's working properly now!