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Swift Academy · Lesson

Properties & Subscripts

Use lazy stored properties, get/set computed properties, property observers, and subscripts for custom indexing.

Intro

This lesson covers advanced properties: lazy, computed with get/set, observers, plus custom subscripts.

lazy property

lazy properties are created only on first access. Useful for expensive work.

struct DataLoader {
    lazy var data: [Int] = {
        print("Loading...")
        return [1,2,3]
    }()
}
var loader = DataLoader()
print("before access")
print(loader.data)

All lessons in this course

  1. Properties & Subscripts
  2. lazy & property observers
  3. Computed properties with get/set
  4. Subscripts for custom indexing
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