swift3 - Swift optional parameter not unwrapped

Question

I have a function with a optional parameter(position). I test for it to be nil but still Xcode shows me an error: "Value of optional type Int? not unwrapped" and suggests me to use "!" or "?".

var entries = [String]()

func addEntry(text: String, position: Int?) {
    if(position == nil) {
        entries.append(text)
    } else {
        entries[position] = text
    }
}

Im new to Swift and don't understand why this isn't ok. Within this if-clause the compiler should be 100% sure that position is defined, or?

Answer 1

There are a few ways to code this properly:

func addEntry(text: String, position: Int?) {
    // Safely unwrap the value
    if let position = position {
        entries[position] = text
    } else {
        entries.append(text)
    }
}

or:

func addEntry(text: String, position: Int?) {
    if position == nil {
        entries.append(text)
    } else {
        // Force unwrap since you know it isn't nil
        entries[position!] = text
    }
}