Pangram checker

You are encouraged to solve this task according to the task description, using any language you may know.
A pangram is a sentence that contains all the letters of the English alphabet at least once.

For example:   The quick brown fox jumps over the lazy dog.



Task

Write a function or method to check a sentence to see if it is a   pangram   (or not)   and show its use.



Related tasks

   determine if a string has all the same characters
   determine if a string has all unique characters


import Foundation
 
let str = "the quick brown fox jumps over the lazy dog"
 
func isPangram(str:String) -> Bool {
    let stringArray = Array(str.lowercaseString)
    for char in "abcdefghijklmnopqrstuvwxyz" {
        if (find(stringArray, char) == nil) {
            return false
        }
    }
    return true
}
 
isPangram(str) // True
isPangram("Test string") // False