In the previous exercise, the function printAllNodes() visited each of the Nodes in the ice cream sequence in an iterative manner, repeatedly setting and then re-setting the value assigned to unwrappedNode. In this exercise, we’ll create a function that also visits each of the Nodes in the ice cream sequence but does so in a different way: recursively.
Instructions
First, define a function called printAllNodesRecursively() with an argument label of startingAt and a parameter of node with an optional type of Node. Leave the body empty.
Let’s start to create the logic needed in our recursive function to visit all the nodes.
Create a constant called node and set it as node, the argument passed into the function.
Here, the printAllNodesRecursively() function should exit with the return keyword when it is passed a node that is nil. (Remember that if you’ve reached a node that is nil in the sequence of Nodes it indicates that there are no Nodes left to visit.)
Change your code declaring the variable node to use a guard statement that checks if the node has a value, and if it is nil, exits from the function with a return.
If the node has a value, you’ll want to print that nodes data. Add this logic on a new line under the guard statement.
Lastly, a recursive function is defined as a function that calls itself. Below the line where you printed node‘s data, call printAllNodesRecursively() with the next Node as the argument.
Test your function. Outside of printAllNodesRecursively(), call it with the first Node in the ice cream sequence, strawberry. You should see all the ice cream flavors print in the terminal.