Generic Extension to Array Not Working - swift

Question

I've been playing around with Generics and Extensions to existing types in Swift 3. I wrote two generic Array functions that extends Array with find-and-replace methods, named replaced() and replace(). The replaced() function works as intended but the replace() function has a compile time error. Here is the code and a test of one of the methods.
extension Array {
func replaced<T: Equatable>(each valueToReplace: T, with newValue: T) -> [T] {
var newArray:[T] = []
for index:Int in 0..<self.count {
if let temp = self[index] as? T, temp == valueToReplace{
newArray.append(newValue)
}else{
newArray.append(self[index] as! T)
}
}
return newArray
}
mutating func replace<T: Equatable>(each valueToReplace: T, with newValue: T) {
for index:Int in 0..<self.count {
if let temp = self[index] as? T, temp == valueToReplace {
// FIXME: self[index] = newValue
}
}
return
}
}
var j = [1,2,3,4,3,6,3,8,9]
var newArray = j.replaced(each: 3, with: 0)
I get a compile time error on the second method, replace(), at the line commented out with "//FIXME:" annotation. The compile time error says, "Ambiguous reference to member 'subscript'".
How can I fix the replace() code so it works?

Answer 1

Give this a shot
extension Array where Element: Equatable {
func replaced (each valueToReplace: Element, with newValue: Element) -> [Element] {
var newArray = [Element]()
newArray.reserveCapacity(self.count)
for element in self {
let newElement = (element == valueToReplace) ? newValue : element
newArray.append(newElement)
}
return newArray
}
mutating func replace(each valueToReplace: Element, with newValue: Element) {
for (i, element) in self.enumerated() {
if element == valueToReplace { self[i] = newValue }
}
}
}
var j = [1,2,3,4,3,6,3,8,9]
var newArray = j.replaced(each: 3, with: 0)
It would be better to remove the redundancy by just making replaced delegate to replace:
extension Array where Element: Equatable {
func replaced(each valueToReplace: Element, with newValue: Element) -> [Element] {
var copy = self
copy.replace(each: valueToReplace, with: newValue)
return copy
}
mutating func replace(each valueToReplace: Element, with newValue: Element) {
for (i, element) in self.enumerated() {
if element == valueToReplace { self[i] = newValue }
}
}
}