Question

I am beginner of CoffeeScript and Jasmine. At first, I tried to pass test with below code:

class Counter
    count: 0

    constructor: ->
        @count = 0

    increment: ->
        @count++

    decrement: ->
        @count--

    reset: ->
        @count = 0

root = exports ? this
root.Counter = Counter

The jasmine test code is below:

describe("Counter", ->
    counter = new Counter
    it("shold have 0 as a count variable at first", ->
        expect(counter.count).toBe(0)
    )

    describe('increment()', ->
        it("should count up from 0 to 1", ->
            expect(counter.increment()).toBe(1)
        )
    )
)

Then kind person told me that the code should be as below:

class Counter
    count: 0

    constructor: ->
        @count = 0

    increment: ->
        ++@count

    decrement: ->
        --@count

    reset: ->
        @count = 0

root = exports ? this
root.Counter = Counter

Yes, this code passed the test. But I have a question that the former code is more natural than latter code. I have no idea how to certain this question. Thank you for your help.

Answer 1

you could change your code to the following to be more clear about return values if you choose to stick to post increment

class Counter
  count: 0

  constructor: ->
    @count = 0

  increment: ->
    @count++
    @count

  decrement: ->
    @count--
    @count
  reset: ->
    @count = 0

root = exports ? this
root.Counter = Counter

or you could change your test to:

describe('increment()', ->
  it("should count up from 0 to 1", ->
    expect(counter.count).toBe(0)
    counter.increment()
    expect(counter.count).toBe(1)
  )
)

but then you don’t expect the returned value of increment and decrement to reflect the updated value of @count

here’s an example to play with that will make the differences obvious:
http://coffeescript.org/#try:class%20Counter%20%20count%3A%200%20%20increment%3A%20-%3E%20%20%20%20%40count%2B%2B%20%20%20%20%40count%20%20%20%20inc%3A%20-%3E%20%20%20%20%40count%2B%2B%20%20decrement%3A%20-%3E%20%20%20%20–%40count%20%20dec%3A%20-%3E%20%20%20%20%40count–cnt%20%3D%20new%20Counteralert%20cnt.increment()alert%20cnt.countalert%20cnt.inc()alert%20cnt.countalert%20cnt.decrement()alert%20cnt.countalert%20cnt.dec()alert%20cnt.count