StringExtensions

Hacking with Swift: 100 Days of Swift - Project 24

Challenges

1. Create a String extension that adds a withPrefix() method. If the string already contains the prefix it should return itself; if it doesn’t contain the prefix, it should return itself with the prefix added. For example: "pet".withPrefix("car") should return “carpet”.
2. Create a String extension that adds an isNumeric property that returns true if the string holds any sort of number. Tip: creating a Double from a String is a failable initializer.
3. Create a String extension that adds a lines property that returns an array of all the lines in a string. So, “this\nis\na\ntest” should return an array with four elements.