Mistake in Apple's Crustacean.playground?

Question

Jens OP

Created Jun ’15

Replies 6

Boosts 0

Views 1.4k

Participants 6

I had a look at the Crustacean.playground (which demonstrates protocol oriented programming), available here:

https://developer.apple.com/swift/resources/

It's a great demonstration but it seems to contain a small mistake in that it says:

// Note: the fact that "rectangleAt" doesn't appear below, but
// "circleAround" does, serves as a demonstration of how dispatching through
// protocols works: methods in protocol extensions that don't match a
// requirement (such as rectangleAt) are dispatched statically.

It is true that "rectableAt" appears above and not below, but there is no "circleAround" at all in the output, and there isn't even any circleAround method, just circleAt, which is not appearing anywhere in the output either.

Tell me if I'm misunderstanding something, or please correct this otherwise great playground.

Boost

Answer 1

jonhull OP

Jun ’15

It looks like 'circleAt' used to be called 'circleAround' but they forgot to change the comments when they renamed the method.

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Answer 2

Jens OP

Jun ’15

It's not only that, it's also that it says:

// Note: the fact that "rectangleAt" doesn't appear below, but 
// "circleAround" does, /.../

while neither circleAround nor circleAt are to be seen anywhere in the output.

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Answer 3

DaveAbrahams OP

Jun ’15

Yes, "circleAround" is a typo—it should be "circleAt"—and the following requirement is missing from Renderer on page 2:

  /// Draws a complete circle with the given center and radius.
  ///
  /// Note: a default implementation of `circleAt` is provided by a
  /// protocol extension, so conforming types need not supply their own.
  func circleAt(center: CGPoint, radius: CGFloat)

Sorry for the inconvenience; we'll try to push an update out ASAP.

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Answer 4

Vision Pro Engineer OP

Apple

Jun ’15

This should be fixed now, please re-download the playground.

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Answer 5

kr1shnak OP

Sep ’17

I was taking a look at the Crustacean.playground today in Xcode 9, and it needed some updates for Swift 4.0.

I've uploaded my changes to github for anyone who needs them:

https://github.com/Krishna/Crustacean---Protocol-Oriented-Programming-in-Swift

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Answer 6

EdwardVS OP

Apr ’18

I've translated Crustacean to a macos project (3 versions)

1) using a storyboard created NSView that implements the renderer protocol

2) a version that programatically creates the window to draw in

3) using a storyboard created NSView that gets the drawing via the cgcontext that implements the protocol

https://github.com/edwardvoss/swift-projects

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