方法中的方法

Question

I am still learning Pharo, but it is a bit confusing. There two classes, CarRental and Car , and a Test class, CarRentalTest .

There are fixed number of cars, the same car cannot be rented twice, I have the code, but there is a mistake.

| carRental redPanda yellowPanda blackTesla |
    carRental := CarRental new.
    redPanda := Car panda.
    yellowPanda := Car panda.
    blackTesla := Car tesla.
    carRental
        addCar: redPanda;
        addCar: yellowPanda;
        addCar: blackTesla.
    self assert: carRental availableCars size equals: 3.
    carRental rent: redPanda days: 5.
    self assert: carRental availableCars size equals: 2.
    self assert: carRental rentedCars size equals: 1

I tried to initialize the availableCars and rentedCard methods, but there is still an issue.

Answer 1

You need to keep track of rented cars, right? To do that add the ivar rented to the CarRental class and initialize it to an empty collection:

rented := OrderedCollection new.

(in other words, include the line above in the #initialize method - instance side.)

Now, every time you rent a car add it to the rented collection:

rent: aCar
  rented add: aCar

and when the car is returned

return: aCar
  rented remove: aCar

Also you can add the getter method which was missing so far

rentedCars
  ^rented

and compute the cars available for rent as

availableCars
  ^cars copyWithoutAll: rented