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Swift Academy · Lesson

Subscripts & custom indices revisited

Define subscripts with get / set , accept multiple parameters (e.g., 2D matrix), and use custom index types (enums) for readable APIs.

What are subscripts?

Subscripts let instances be indexed like arrays. You can:

  • Expose read-only or read–write access
  • Accept multiple parameters (e.g., row/col)
  • Use custom indices like enums for clarity

Read-only subscript

A subscript can be read-only by returning a value without set.

struct TimesTable {
    let multiplier: Int
    subscript(index: Int) -> Int { multiplier * index } // read-only
}
let t = TimesTable(multiplier: 3)
print(t[4]) // 12

All lessons in this course

  1. Operator overloading & precedence groups
  2. Subscripts & custom indices revisited
  3. Hashable/Equatable/Comparable derivations
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