problems on using the if and else statement and updating the data.

[Mr.Nobody645]

Right now Im new to this programming and Im having the problems of using the if and else statement on (data && data). Next is the update part which i really dont get it. Saw a lot of videos of using MySQL instead of normal programming update. So here is my code

f (ui-> AddOn1 -> isChecked()){
        price = 2.50;
    }
    else if (ui-> AddOn2 -> isChecked()){
        price = 1.20;
    }
    else if (ui-> AddOn3 -> isChecked()){
        price = 1.10;
    }
    else if (ui-> (AddOn1 + AddOn2 )-> isChecked()){
        price = 3.70;
    }
    else if (ui-> (AddOn1 + AddOn3 )-> isChecked()){
        price = 3.60;
    }
    else if (ui-> (AddOn2 + AddOn3) -> isChecked()){
        price = 2.30;
    }
    else if (ui-> (AddOn1 + AddOn2 + AddOn3) -> isChecked()){
        price = 4.80;
    }




    total = price;
    total = ui -> lbTotal ->text().toDouble()+price;
    ui ->lbTotal->setText(QString::number(total,'f',2));

[JonB]

@Mr-Nobody645
if ... else is just C++.

In principle your code approach looks about what is necessary.

But what in the world is

else if (ui-> (AddOn1 + AddOn2 )-> isChecked()){

supposed to be?? Is it maybe:

else if (ui-> AddOn1-> isChecked() && ui-> AddOn2-> isChecked()){

? In which case you'll need to test that before testing ui-> AddOn1-> isChecked() or ui-> AddOn2-> isChecked() individually.

You should read up on basic C++/programming. It's not to do with Qt, and you won't be able to do anything effectively in Qt (or any other toolkit) if you have simple programming issues. I realize this is your first post, but very kindly/helpful advice you should know that programming issues are better dealt with as such than on a Qt-specific forum.

[sierdzio]

Do you actually want to ask some question here? What is your problem?

Do you mean to ask how to check multiple values at once in an if statement?

ui-> (AddOn1 + AddOn2 + AddOn3) -> isChecked()

Here is something which should work:

if (ui->AddOn1->isChecked() && ui->AddOn2->isChecked() && ui->AddOn3->isChecked())

But for sake of readability and maintenance (and, to some degree, performance), I'd suggest to get state first, and check later:

const bool isAddOn1 = ui->AddOn1->isChecked();
const bool isAddOn2 = ui->AddOn2->isChecked();
const bool isAddOn3 = ui->AddOn3->isChecked();
if (isAddOn1 && isAddOn2 && isAddOn3)
// ...

All modernt compilers also understand and as a synonym to && so you can do:

if (isAddOn1 and isAddOn2 and isAddOn3)

[Mr.Nobody645]

omg ty for the if and else part. Really appreciate your help.

[Mr.Nobody645]

im appreciate for both of you on helping me in the if and else part. However, when i try to checked AddOn1 and AddOn2, i got my price 2.50 instead of 3.70.

[J.Hilk]

@Mr-Nobody645 said in problems on using the if and else statement and updating the data.:

im appreciate for both of you on helping me in the if and else part. However, when i try to checked AddOn1 and AddOn2, i got my price 2.50 instead of 3.70.

obviously, as

if (ui-> AddOn1 -> isChecked()){
price = 2.50;
}

comes before everything else and its true so the rest of the checks is not executed

[JonB]

@Mr-Nobody645 said in problems on using the if and else statement and updating the data.:

However, when i try to checked AddOn1 and AddOn2, i got my price 2.50 instead of 3.70.

That's why I wrote earlier:

In which case you'll need to test that [if (ui-> AddOn1-> isChecked() && ui-> AddOn2-> isChecked())] before testing ui-> AddOn1-> isChecked() or ui-> AddOn2-> isChecked() individually.

[JonB]

@sierdzio said in problems on using the if and else statement and updating the data.:

All modernt compilers also understand and as a synonym to && so you can do:

I am speechless! Apart from the fact that I have never heard of this (old time C/C++ programmer, now returned to new C++). And apart from the fact that introducing and as a language keyword would potentially break one million old C/C++ programs which could have used and as a variable?

You are obviously more expert than I, but do you want to recommend this to a newbie? I have never noticed and used in a C++ program, if OP is to produce standard code, and recognize others' code, would you not recommend sticking with &&?

[J.Hilk]

@JonB apparently part of the standard since c++98
https://en.cppreference.com/w/cpp/keyword/and

[JonB]

@J-Hilk , @sierdzio
Absolutely shocking! I see from https://en.cppreference.com/w/cpp/language/operator_alternative that there are actually 11 new reserved words for operators. Including not, and even the string compl, which I might have used as variables and would break upgrading to C++ '98.

Thinking aloud, I believe all C operators were symbols and not words, part of the charm (for right or for wrong) of the language.

With all due respect to @sierdzio's comment, which I accept & respect, I have still never seen a piece of C++ code using any of these.... [And hence would caution a beginner against adopting these.]

[C++ looks like it's trying to be a Python-wannabe ;-) ]

[jsulm]

@JonB said in problems on using the if and else statement and updating the data.:

I have still never seen a piece of C++ code using any of these

Me neither :-)

[sierdzio]

I have seen it but very, very rarely.

And hence would caution a beginner against adopting these

I'm split on this :D One one hand, && is clearly, vastly, totally the established and well-known convention practically everywhere. So using it is definitely a good idea.

But on the other hand, and is more readable and convenient. So it is also a good idea.

[JonB]

@sierdzio said in problems on using the if and else statement and updating the data.:

But on the other hand, and is more readable and convenient.

In Pascal or Python, yes. When scanning C/C++ I expect to see all operators as symbols (and not some but not others) Next C++ will be offering begin/end for {/}! [Some people used to do all this words-for-symbols via C #defines.] I give up on the modern world, it's all going to pot... ;-)

[J.Hilk]

@JonB said in problems on using the if and else statement and updating the data.:

Next C++ will be offering begin/end for {/}!

you can use

{	??<
}	??>
[	??(
]	??)
#	??=
\	??/
^	??'
|	??!
~	??-

but that was removed in c++17, :)

[JonB]

@J-Hilk

but that was removed in c++17, :)

Even better --- you start using new language constructs and then they remove them so that your code gets broken!

FWIW, I note from https://en.cppreference.com/w/cpp/language/operator_alternative

There are alternative spellings for several operators and other tokens that use non-ISO646 characters.

So the motivation never was "clarity", it's to do with people having funny keyboards....

[SGaist]

@JonB said in problems on using the if and else statement and updating the data.:

funny keyboards

The hardware is innocent ;-P

[Kent-Dorfman]

whats next, espousing the virtues of trigraphs?

[1Manui1]

How did you do it now?