Swift Subscript

Subscript in Swift is a shortcut for accessing elements of a collection, list, or sequence. It is syntactic sugar that allows the use of the subscript syntax [] to access elements. Subscripts can also be defined in custom types, with syntax similar to computed properties. Multiple subscripts can be defined with different input parameters and return types.

Syntax

The syntax for defining a subscript in Swift is as follows:

subscript(index: Int) -> Int {
  get {
    // Return an appropriate subscript value here
  }

  set(newValue) {
    // Perform a suitable setting action here
  }
}

• subscript(index: Int) -> Int: This defines a subscript that takes an Int parameter (index) and returns an Int value.
• get: The getter block should return the value corresponding to the index.
• set: The setter block should set a new value at the specified index.

Example

This example creates a TimesTable structure with a subscript that returns the product of the multiplier and the index. The subscript is accessed using the [] syntax to compute the result:

struct TimesTable {
  let multiplier: Int
  subscript(index: Int) -> Int {
    return multiplier * index
  }
}

let threeTimesTable = TimesTable(multiplier: 3)
print("Six times three is \(threeTimesTable[6])")

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The above code produces the following output:

Six times three is 18

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