Dictionary Basics: Ice Cream

Objectives

1. Practice creating and using a dictionary.
2. Write methods to interpret the information in a dictionary.
3. Practice converting to a mutable dictionary and modifying it programmatically.

Introduction

Some of the instructors are planning a summer ice cream party. Mark has collected some information on everyone's favorite ice cream flavors (including his own), but he needs help analyzing the list to know how much of each flavor to buy!

Joe likes Peanut Butter and Chocolate
Tim wants Natural Vanilla
Sophie loves Mexican Chocolate
Deniz only likes Natural Vanilla
Tom will eat Mexican Chocolate
Jim never answered so he's getting Natural Vanilla
Mark — Cookies 'n Cream duh

Instructions

1. Open the *.xcworkspace file and without looking at the tests just yet, navigate to the FISAppDelegate.h header file and declare two methods:

• namesForIceCream: which takes an NSString argument iceCream and returns an NSArray object.
• countsOfIceCream: which takes an NSDictionary argument iceCreamByName and returns an NSDictionary object.

2. In the FISAppDelegate.m implementation file, use autocomplete to define the method bodies to return nil. At the start of the namesForIceCream: method, translate Mark's notes into an NSDictionary with each name as a key with that person's preferred ice cream flavor as the associated value.

3. When you're done, check your work by looking at the iceCreamByName dictionary in the FISAppDelegateSpec test file. Your dictionary's key-value pairs should match it exactly, but don't just copy/paste it—really try to compose the dictionary yourself. Run the tests now to see that they fail.

4. Finish the namesForIceCream: method body to return an array of the names of everyone who likes the ice cream flavor submitted in the string argument. For example, "Mexican Chocolate" should return an array with "Sophie" and "Tom".

5. Write the countsOfIceCream body which returns a dictionary of the number (value) of people who like each flavor of ice cream (key). Look at the countsByIceCream dictionary in the FISAppDelegateSpec file to better understand what the test is expecting.
   Hint: Try using the namesForIceCream: method that you just wrote to get a list of names for each ice cream flavor by calling it on self. This method returns an array of names which you can then count. Remember that you have to convert integer values to NSNumber in order to store them in a collection.

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