Checks to see if a given sentence is a Pangram

Check for Pangram in Swift.swift

func isPangram(string: String) -> Bool {
    let alphabet = "abcdefghijklmnopqrstuvwxyz"
    let lowerCaseString = string.lowercased()
    
    for letter in alphabet {
        if !lowerCaseString.contains(letter) {
            return false
        }
    }
    
    return true
}