Answer by Martin R for How to remove special characters from string in Swift 2?

In Swift 1.2,

let chars = Set("abcde...")

created a set containing all characters from the given string. In Swift 2.0 this has to be done as

let chars = Set("abcde...".characters)

The reason is that a string itself does no longer conform to SequenceType, you have to use the characters view explicitly.

With that change, your method compiles and works as expected:

func removeSpecialCharsFromString(str: String) -> String {
    let chars = Set("abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLKMNOPQRSTUVWXYZ1234567890+-*=(),.:!_".characters)
    return String(str.characters.filter { chars.contains($0) })
}

let cleaned = removeSpecialCharsFromString("ab€xy")
print(cleaned) // abxy

Remark: @Kametrixom suggested to create the set only once. So if there is performance issue with the above method you can either move the declaration of the set outside of the function, or make it a local static:

func removeSpecialCharsFromString(str: String) -> String {
    struct Constants {
        static let validChars = Set("abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLKMNOPQRSTUVWXYZ1234567890+-*=(),.:!_".characters)
    }
    return String(str.characters.filter { Constants.validChars.contains($0) })
}