Subscripts
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Subscript Syntax
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subscript(index: Int) -> Int {
get {
// Return an appropriate subscript value here.
}
set(newValue) {
// Perform a suitable setting action here.
}
}
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subscript(index: Int) -> Int {
// Return an appropriate subscript value here.
}
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struct TimesTable {
let multiplier: Int
subscript(index: Int) -> Int {
return multiplier * index
}
}
let threeTimesTable = TimesTable(multiplier: 3)
print("six times three is \(threeTimesTable[6])")
// Prints "six times three is 18"
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Subscript Usage
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var numberOfLegs = ["spider": 8, "ant": 6, "cat": 4]
numberOfLegs["bird"] = 2
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Subscript Options
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struct Matrix {
let rows: Int, columns: Int
var grid: [Double]
init(rows: Int, columns: Int) {
self.rows = rows
self.columns = columns
grid = Array(repeating: 0.0, count: rows * columns)
}
func indexIsValid(row: Int, column: Int) -> Bool {
return row >= 0 && row < rows && column >= 0 && column < columns
}
subscript(row: Int, column: Int) -> Double {
get {
assert(indexIsValid(row: row, column: column), "Index out of range")
return grid[(row * columns) + column]
}
set {
assert(indexIsValid(row: row, column: column), "Index out of range")
grid[(row * columns) + column] = newValue
}
}
}
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var matrix = Matrix(rows: 2, columns: 2)
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matrix[0, 1] = 1.5
matrix[1, 0] = 3.2
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func indexIsValid(row: Int, column: Int) -> Bool {
return row >= 0 && row < rows && column >= 0 && column < columns
}
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let someValue = matrix[2, 2]
// This triggers an assert, because [2, 2] is outside of the matrix bounds.
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Type Subscripts
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enum Planet: Int {
case mercury = 1, venus, earth, mars, jupiter, saturn, uranus, neptune
static subscript(n: Int) -> Planet {
return Planet(rawValue: n)!
}
}
let mars = Planet[4]
print(mars)
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