Error unknown typ name 'DS18B20'

AlexKrammer

@mrjj
i dont want to update NUM outside..
look one post above. I edited it

mrjj

CheckTemperature
{
     float example;
     TEST c;
     example  = c.NUM;
     //example still 0
}

Yes as you make a local TEST c variable
so if you did if you did c.NUM=100
somewhere else its not the same TEST instance.

So TEST c; should be a member if you want to set its NUM outside of CheckTemperature

then it works.

AlexKrammer

@mrjj
yes i did it?
i created a object of Test in MainWindow
then i put c.NUM = 100;

after that i created a object of Test in CheckTemperature too
but c.NUM dont have 100. Its still have 0.

jsulm

@AlexKrammer So, you create two instances of Test, change one of them and expect the other one to have the same change? How? By magic? Maybe I don't get something as the thread is already quite long...

Test a;
Test b;
a.NUM = 100;
// Why should b.NUM be 100 now?!

AlexKrammer

@jsulm
where do i create two instaces of Test? I only create a Object of TEST with c. change the Variable NUM and try to get c.NUM in a other Class

class TEST{
int NUM = 0;
}

MainWindow{
TEST c;
c.NUM = 100;
}

CheckTemperature
{
float example;
TEST c;
example = c.NUM;
//example still 0
}

Or do i change the value of the variable in the object TEST c (c.NUM) i created? Not the Variable in the class TEST

jsulm

@AlexKrammer said in Error unknown typ name 'DS18B20':

where do i create two instaces of Test?

In the code you just posted (hint: instance is the same thing as object):

MainWindow{
TEST c; // First instance
c.NUM = 100;
}

CheckTemperature
{
float example;
TEST c; // Second instance, c here is NOT the same as in MainWindow!
example = c.NUM;
//example still 0
}

mrjj

@jsulm said in Error unknown typ name 'DS18B20':

TEST c; // First instance

This has to go in .h , in the MainWindow class and then

TEST c; // Second instance, has to be removed then
its the same and it should work.

AlexKrammer

@mrjj
If i create in MainWindow.h a instance called TEST c;

That instance won't work in class CheckTemperature. Will it?

mrjj

@AlexKrammer
No as its 2 different instances. one in MainWin and one in CheckTemperature.
They are not the same.

AlexKrammer

@mrjj
And is there a posibility to use a variable of a class in 2 other classes

mrjj

@AlexKrammer
Yes if you use a pointer or reference then it will point back to the original variable.

like

int Num=0; the actual one

class Test() {
int &NumRef;
void Test( int MyNum ) : NumRef(MyNum) {}
}

then when you create the instance

Test MyTest(Num);

Then it points to the actual one and will always have the same value.

But often its not the best idea and can be solved other way like give it directly when you want to
other classes to use the data.

class Test() {
int DoSomething(int NumTouse);
}

Test c;
int result = c.DoSomething(Num);

AlexKrammer

@mrjj well thank you very much. My problem has been fixed and about this problem i'm going to read something on a c++ article.
Thanks for your time.

mrjj

@AlexKrammer
Good to hear and you are welcome.
Its a good idea to read up on c++ as Qt uses it a lot and
its best to have good understanding on some of the concepts as not to feel really uphill:)