Questions using events

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Questions using events

• By Deborah Nelson
• Duke University
• Under the direction of
• Professor Susan Rodger
• July 31, 2008

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Loading the world

• Download the starting world.
• It is called questionEventStart.a2w.
• Save it in a directory that you can find again.
• After you have opened the file go into the
  "Layout" mode by clicking on the green button Add
  Objects (toward the middle of screen).
• Click more controls. Click drop a dummy at the
  camera. Rename the dummy originalPosition. To
  leave the layout mode, click done.

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Overview

• The purpose of this tutorial is to provide a
  template for a quiz in which the user clicks on a
  different object to answer each question.
• We are going to create the following in this
  tutorial
• Two world-level property variables
• Three world-level methods
• One world-level function

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Creating property variables

• In the world details pane, go to properties, and
  click create new variable.
• Name it correctAnswer. Select type Object.

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• Click create new variable again.
• Name this one userAnswer, and select type Object.
• These variables will be used in each of the
  methods we are going to write.

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Quiz Method

• Now, create a new world method, and name it
  quiz1.

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Part 1 Writing quiz1 method

• In this example world, the teacher asks each
  question.
• Step 1 For the first question, click on the
  teacher in the object tree. Drag the teacher say
  method into the quiz1 method, select other and
  type in Which animal says meow? Click on that
  animal. Set the duration to 2 seconds.
• The next step is to store the correct answer in
  our correctAnswer variable. See the next slide!

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Storing the correct answer

• Step 2 Click on the properties tab in the world
  details pane. Drag correctAnswer into the quiz1
  method
• In the drop down menu, select set value, cat,
  and the entire cat.
• See the screenshot on the next slide for an
  illustration.

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• Resulting Code

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• Step 3 Drag a while from the bottom of the
  window into your quiz1 method.
• In the drop down menu, select true.

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• Click on the properties tab in the world details
  pane.
• Drag correctAnswer on top of the true part of the
  While loop.
• Step 4 In the drop down menu, select
• correctAnswer !, expressions, and
  world.userAnswer.
• -! means does not equal.
• See the screenshot on the next slide for an
  illustration

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• Resulting code

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• Step 5 Finally, drag a Wait from the bottom of
  the window to the end of quiz1 method.
• Select 2 seconds in the drop down menu.

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• Repeat Part 1, steps 1-5 for question 2 Which
  animal hops?
• The answer is bunny.
• Your resulting code should look like the
  screenshot on the following slide.

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Calling Quiz1

• Click on the world.my first method tab.
• Click on the methods tab in the details pane.
  Drag quiz1 into world.my first method.

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Playing your world

• Click on the properties tab in the world details.
  
• Play your world. The correctAnswer variable
  changes to cat after the teacher asks her
  question.

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Part 2 Storing the users answer

• We will now write code to store the users
  answer.
• Click on the function tab, create a new function,
  name it possibleChoices, and select type Boolean.
  Boolean returns true or false.

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Create a new parameter

• Click on create new parameter in the
  world.possibleChoices function.
• Name it objClicked. Select type Object.

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• Step 1Drag an If/else from the bottom of the
  window and drag it into the function. Select true
  in the drop down menu.
• Step 2 Drag the parameter objClicked onto the
  true. In the drop down menu, select objClicked
  , cat, and the entire cat.
• See the screenshot on the next slide for an
  illustration.

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• Resulting code

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• Step 3 drag Return from the bottom of the window
  on top of the Do Nothing under the If.
• Click on the ltNonegt beside return and select true.

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• Step 1 Drag an If/else on top of the Do Nothing
  under the Else.
• Select true in the drop down menu.
• Step 2 Drag the parameter objClicked on top of
  the true. And select objClicked, bunny, and the
  entire bunny.
• Resulting code

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• Step 3 Drag in Return under If objClicked
  Bunny. Select true.
• Repeat Part 2, steps 1-3 for T-rex.
• Repeat Part 2, steps 1-3 for cow.
• The rest of your nested If statements should look
  like this

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• Drag Return on top of the final Do Nothing.
  Select false in the drop down menu.
• Dont forget to set the final Return to false.

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Compare method

• In the world details pane, click on the method
  tab. Click create new method. Name it compare.
• Drag an If/Else from the bottom of the window,
  and select true. Click on the functions tab and
  drag the function possibleChoices on top of the
  true.

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• Click on the properties tab in the world details
  pane.
• Drag userAnswer on top of the ltNonegt next to
  world.possibleChoices.

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• Drag another If/Else on top of the Do Nothing
  underneath the If, and select true. Then drag
  userAnswer onto the true, select userAnswer!,
  expressions, and world.correctAnswer.
• Resulting Code

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• Drag the userAnswer property from the properties
  pane, on top of the Do Nothing underneath this
  second If.
• Select the say method. Type I am not the correct
  answer.

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The else

• Drag a Do together from the bottom of the window
  into the Do Nothing underneath the Else.
• Drag the teacher say method into the code. Select
  other and type Good job. Thats right
• Drag the userAnswer into the Do together and
  select turn left 1 revolution.
• See the screenshot on the next slide for an
  illustration.

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• In the final Else, drag the teacher say method
  into it. Select other and type Click on the
  object to answer the question.
• Change the duration to 1.5 seconds.
• See the screenshot on the next slide for the
  complete method.

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ChooseObject method

• Next, write the method to call this compare
  method. Click create new method in the world
  details pane.
• Name it chooseObject.
• Click create new parameter in this method. Name
  it objClicked. Select type Object.

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• Click on the properties tab in the world details
  pane. Drag userAnswer into the chooseObject
  method. Select set value, expressions, and
  objClicked.

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• Click on the methods tab. Drag compare into the
  chooseObject method.
• This is the complete method.

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Calling the chooseObject method Making an event

• In the events editor, click on create new event,
  and select When the mouse is clicked on
  something.

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• Click on the methods tab in the world details
  pane.
• Drag the chooseObject method on top of the
  Nothing in the event.

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• In the drop down menu, select expressions, and
  object under mouse cursor.
• Here is the complete event

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Play your world

• After the teacher asks the first question, click
  on the cat for your answer to make sure all of
  your methods work.
• To test all of your If statements, after the
  teacher asks the second question, click on a
  wrong answer. Then click on anything in the world
  that is not an animal.

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Practice

• The steps in this tutorial are useful for
  answering questions with the click event.
• Go back to quiz1 method. Using steps 1-5 from
  Part 1 of this tutorial, ask these two questions
• -Which animal is extinct? (the T-Rex)
• Which animal can be milked? (the cow)

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Further practice

• Drag the camera set point of view instruction
  into your world.my first method. Select Dummy
  Objects, and Quiz2View.
• Create a new world method named quiz2.
• In quiz2, ask questions about each of the shapes
  using the same format as quiz1.
• Keep in mind that you will also have to revise
  your possibleChoices function in order to include
  the shapes.

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Recap

• Two world-level property variables are used to
  store the correct answer and the users answer.
• To begin, the correct answer is set. Until the
  users answer equals the correct answer, an empty
  While loop keeps the next question from being
  asked (world.quiz1).
• When the user clicks on an object, a method is
  called to store that object as their answer
  (world.chooseObject), as long as they clicked on
  one of the choices (world.possibleChoices).
• Then, a method is used to compare the users
  answer to the correct answer (world.compare) .