All language subtitles for 5. Checking User Answers

So notice that all that we did, is we created a list of questions where we copied over the questions
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from down here and we've only got three of them.
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And then we created a variable to track where we are in the list of questions,
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and it starts from zero. And then down here where we have our text widget, the text that we chose to display
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in it comes from our list of questions pulling in the item at this particular index. And then down
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here, in our onPressed for our true and false buttons, we use set state to update our question number
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and update the screen when the user presses the true or the false buttons.
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Now we can use the hot restart,
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then we reset our question number back down to zero. And we can cycle through our questions until we
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run out of questions at which point we get a range error because we don't have any more questions to
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display.
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So now that we've done that, the next part is to create a list of matching answers.
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So right below our questions here, we're going to create a list of booleans, because these are going to
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be our answers.
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And this is also going to be a list, and it's going to correspond to the questions. So we can see that
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the first question's correct answer is false,
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and the second question is true and then the third is true.
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So in our list of answers, we're going to listed in that order.
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So again we say false, true, true.
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So now, at the same index, our answers match our questions. At index 0
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is this question and it's correct answer is false.
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So now we can check to see if the user got the right answer. Inside our onPressed,
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we're going to figure out if the user got the answer right or if they got it wrong. In order to do this,
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we're first going to figure out what the correct answer was.
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So let's create a new variable and it's going to hold data type of boolean.
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And this is going to be called correct answer.
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Now the correct answer of course comes from our list of answers, and we're going to pull out the answer
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at the current question number.
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So we're gonna say answer, and inside a set of square brackets, we're going to provide the question number.
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So that means that when the user is seeing 'You can lead a cow downstairs but not upstairs', then
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question number has to be equal to 0, because it starts off being 0.
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And so when we look inside the answers list and we try to get the one at index 0, then that's the correct
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answer for that question.
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So now that we've got the correct answer, all we have to do is to check to see if what the user picked,
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which in this case is true, is equal to the correct answer.
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So we can use something called an if-statement, and inside these parentheses, we're going to check to
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see if the user-picked answer, which in this case is true, is equal to the correct answer.
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So we can say correctAnswer == true. Then that means the user got it right.
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So we can print into the console, we can write user got it right.
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But if they didn't get it right, then we're going to print user got it wrong.
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If the correct answer is equal to the button that they picked, which is true, then we're going to print
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they got it right,
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otherwise we gonna print
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they got it wrong.
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And then down here at the other button, and this is the false button,
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if they clicked on this button then we want to check if the correct answer is equal to false. Then that
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means they got it right,
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otherwise it means they got it wrong.
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Now you have to make sure that this set of code goes before we increase the question number and we go
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to the next question. Because we want to check the correct answer for the current question and make sure
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that those two match.
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Now if we go ahead and click hot restart to take our question number back down to zero and start on question
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1,
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then you can see that this is the question. And if I click on true, that's my selection, then it tells
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me that I got it wrong because the actual correct answer for the first question is false.
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Now let's go onto the next one.
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Let's try and get this one right.
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Let's check out the answer.
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So this one, the correct answer is true.
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So if I click on the true button, it tells me that I got it right.
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And the final one is also a true.
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So if I click on the false button, it tells me that I got it wrong, but then it crashes because it tries
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to go to the next question, and we don't have another question.
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So although this works, if we had more data for each question, say if we had instead of just true and
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false, we had you know a multiple choice question or for each question we even had a picture that's associated
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with it, then we would end up creating many many lists and try to make sure that we're always matching
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the right item in these different lists.
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And that's quite error prone.
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So we're going to upgrade our questions and answers a little bit later on.
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But first for those you guys who have never seen this syntax these if and else, or what we call conditionals
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in programming, then the next lesson is all about that and we discuss how to use if and else statements in
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Dart, and how to build up an elseif leader using Dart as well.
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So if this is unfamiliar to you, then you might find the next lesson really helpful to get a better understanding
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of this.
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But if you're already familiar with how if and else works, then feel free to skip to the next lesson where
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we're going to build a class for our questions.