https://github.com/below/codersample

A Question About Swift and NSCoding
https://github.com/below/codersample

Last synced: about 1 year ago
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A Question About Swift and NSCoding

• Host: GitHub
• URL: https://github.com/below/codersample
• Owner: below
• License: mit
• Created: 2017-06-11T07:35:05.000Z (almost 9 years ago)
• Default Branch: master
• Last Pushed: 2017-06-12T11:55:14.000Z (almost 9 years ago)
• Last Synced: 2025-01-26T02:44:22.331Z (about 1 year ago)
• Language: Swift
• Size: 8.79 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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# A Question About Swift and NSCoding

## Solved: 

Assuming that you provide default values for any new properties you introduce in a subclass, the following two rules apply:

Rule 1

If your subclass doesn’t define any designated initializers, it automatically inherits all of its superclass designated initializers.

Rule 2

If your subclass provides an implementation of all of its superclass designated initializers—either by inheriting them as per rule 1, or by providing a custom implementation as part of its definition—then it automatically inherits all of the superclass convenience initializers.

https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Initialization.html#//apple_ref/doc/uid/TP40014097-CH18-ID216

It appears that when a class adheres to the `NSCoding` protocol, it also **must** have an `init` method even when it is, say, inheriting from `NSObject`

Why is that the case?

Providing boilerplate code will make the compiler happy: 

```swift

    override init () {

        super.init()

    }

```

This looks like syntactic sugar to me, and I don't expect this in Swift: An `init` method exists, apparent by the `override` keyword, and my method does nothing but call `super`. Yet, it is necessary.

What am I missing? Or is this a bug?

Oh, yes both Swift 3 and 4