Map an array with a function with two arguments - Swift - arrays

Question

Is it possible to map an array with a function that takes in two arguments?
Something like this:
let arr = [2,5,1,4,8,4]
let bankRateArr = arr.map(BankRate.init(amount:interestRate:))
class BankRate {
let amount: Int
let interestRate: Float
init(amount: Int, interestRate: Float) {
self.amount = amount
self.interestRate = interestRate
}
}

Answer 1

If you want to pass the same interest rate to all values, you can do:
class BankRate: CustomStringConvertible {
let amount: Int
let interestRate: Float
init(amount: Int, interestRate: Float){
self.amount = amount
self.interestRate = interestRate
}
var description: String {
return "amount: \(amount), rate: \(interestRate)"
}
}
let arr = [2, 5, 1, 4, 8, 4]
let bankRateArr = arr.map { BankRate(amount: $0, interestRate: 0.04) }
print(bankRateArr)
Output:
[amount: 2, rate: 0.04, amount: 5, rate: 0.04, amount: 1, rate: 0.04, amount: 4, rate: 0.04, amount: 8, rate: 0.04, amount: 4, rate: 0.04]
If you want each to have their own, you can do it with tuples:
let arr2 = [(2, 0.04), (5, 0.07), (1, 0.1), (4, 0.035), (8, 0.25), (4, 0.2)]
let bankRateArr2 = arr2.map { BankRate(amount: $0.0, interestRate: Float($0.1)) }
print(bankRateArr2)
Output:
[amount: 2, rate: 0.04, amount: 5, rate: 0.07, amount: 1, rate: 0.1, amount: 4, rate: 0.035, amount: 8, rate: 0.25, amount: 4, rate: 0.2]
And thanks to Martin R, the 2nd example can be shorted a bit as:
let arr3: [(Int, Float)] = [(2, 0.04), (5, 0.07), (1, 0.1), (4, 0.035), (8, 0.25), (4, 0.2)]
let bankRateArr3 = arr3.map(BankRate.init)
print(bankRateArr3)

Answer 2

Assuming that you will have two separate arrays
let amounts = [2, 5, 1, 4 ,8 ,4]
let rates: [Float] = [0.1, 0.2, 0.3, 0.4, 0.5, 0.6]
you could use
let bankRates = zip(amounts, rates).map(BankRate.init)