分割字符串

var a = "a, b, c, d, e, f"

let array = a.components(separatedBy:",")

最后结果：

array = ["a"," b"," c"," d"," e"," f"]

去掉空格

let newArray = []

for string in array {

let whitespace = NSCharacterSet.whitespaces

let str: String = string.trimmingCharacters(in: whitespace)

newArray.append(str)

}

最后结果：newArray = ["a",“b","c","d","e","f"]

字符串截取

三种方式： 1） subString（from：50）

                    2） substring（to：50）

                    3）substring（with：NSMakeRange(50, 8)）