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Practice Object Interaction

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Explanation: Revisiting the checkOut() and returnBook() Methods

1:42 with Ashley Boucher

Now that we've fleshed out our classes and objects and updated our plan of attack, let's revisit writing the `checkOut()` and `returnBook()` methods on the Patron class.

Instructions for Workspace

Your instructions are as follows:

1) Inside the Patron class, add two methods: checkOut() and returnBook()

  • The checkOut() method should receive one argument, a Book object.
  • It should update the currentBook property to the Book object that's passed in.
  • It should update that Book object's out property to true.
  • It should update that Book object's patron property to the Patron object itself
  • It should calculate the due date (14 days in the future) and then set the Book object's dueDate property to that due date.



  • The returnBook() method should receive one argument, a Book object.
  • It should update the currentBook property to null
  • It should update that Book object's out property to false
  • It should update that Book object's patron property to null
  • It should update that Book object's dueDate property to null

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    [MUSIC] 0:00
    Now that the book and patron classes have been fleshed out a little more, 0:04
    let's keep going with the patron class methods we discussed earlier. 0:08
    Check out and return book. 0:11
    The check out method is going to utilize all of the things we did in 0:14
    this last stage. 0:16
    This method will receive one argument, a book object. 0:18
    What do you think will happen next? 0:21
    Well, first we should set the patron's current book property 0:23
    to the book object that was passed in. 0:26
    This way, when a library employee looks up a patron, 0:28
    they will see what book, if any, that patron has checked out. 0:31
    Then we can set all the associated properties on the book object. 0:35
    Its out property should be set to true. 0:39
    It's patron property should be set to the patron object itself. 0:42
    That can be accomplished by setting the property to the this keyword. 0:46
    This, when used by itself inside a class, refers to the entire object. 0:50
    Finally, the book's dueDate property should be calculated and set. 0:55
    For our purposes, books will be due two weeks, or 14 days, from checkout. 0:59
    The return book method, is basically the inverse of the check out method. 1:05
    The book that's being returned, is passed in as an argument, 1:09
    the patron's current book property should be set back to null, 1:12
    since they're no longer borrowing the book. 1:15
    The book should be marked back in, and 1:17
    as a result, its due date property will be set back to null. 1:19
    Then we set the book's patron property back to null as well. 1:22
    I've attached a work space to this video. 1:26
    Open it up and try to code these out on your own. 1:29
    There's a read me file inside the work space with detailed instructions. 1:31
    When you're done, or if you get stuck, head to the next step to see the solution. 1:35
    Remember, everything you're doing is just for practice. 1:39

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