Beginner Swift: Converting string if letter in dictionary - swift

Question

Thanks for your help - just starting out so imagine there's some serious issues with my logic here.
Trying to write a program, given an input, if a letter from that input is found in a dictionary, replace the letter with the corresponding value.
Really stuck where I'm going wrong. Anyone able to help / suggest an alternative logic that may work?
var leetDic = ["A" : "4",
"B" : "6",
"E" : "3",
"I" : "1",
"L" : "1",
"M" : "(V)",
"N" : "(/)",
"O" : "0",
"S" : "5",
"T" : "7",
"V" : "(/",
"W" : "`//]"]
func leetConverter(leet: String) {
var leet1 = leet.uppercased()
for i in leet1.characters {
if i == leetDic.keys { //ERROR "Binary operator cannot be applied to operands of type Character and dictionary"
i = leetDic.values // ERROR "cannot assign value 'i' is a let constant"
} else {
return i
}
}
}
var test = leetConverter(leet: "Hello World")

Answer 1

Problem is you are comparing character and array also you can assign value to i in loop because it is constant you can go like this way.
func leetConverter(leet: String) -> String {
var leet1 = leet.uppercased()
var newString = String()
for ch in leet1.characters {
let str = String(ch)
if let value = leetDic[str] {
newString.append(value)
} else {
newString.append(str)
}
}
return newString
}
More Swifty way
func leetConverter(leet: String) -> String {
let str = leet.characters.map { leetDic[String($0).uppercased()] ?? String($0) }.joined()
return str
}