Looping with while loops

for loops are great when you know how many times you intend to loop, but if you want to loop until a certain condition is met, you need a while loop.

A while loop has the following syntax:

while <#boolean expression#> { 
    <#code to execute#> 
} 

The code block will execute over and over until the Boolean expression returns false. Therefore, it's a common pattern to change some value in the code block that may cause the Boolean expression to change to false.

If there is no chance of the Boolean expression becoming true, the code will loop forever, which can lock up your app.

In this recipe, we will look at situations where a while loop can be useful for repeating actions.

Getting ready

This recipe will involve simulating the random flip of a coin. To flip our coin, we will need to randomly pick either heads or tails, so we will need to use a random number generator from the Foundation framework. We will discuss Foundation further in Chapter 5...