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?