Unity 5.x Cookbook: More than 100 solutions to build amazing 2D and 3D games with Unity

Many games involve the player collecting items or choosing from a selection of items. Examples could be collecting keys to open doors, collecting ammo for weapons, choosing from a collection of spells to cast, and so on.

The recipes in this chapter offer a range of solutions for displaying to the player whether they are carrying an item or not, if they are allowed more than one of an item, and how many they have.

This recipe presents the steps to create the 2DSpaceGirl mini-game, on which all the recipes of this chapter are based.

Often the simplest inventory situation is to display text to tell players if they are carrying a single item (or not).

Graphic icons are an effective way to inform the player that they are carrying an item. In this recipe, if no star is being carried, a grey-filled icon in a blocked-off circle is displayed; then, after the star has been picked up, a yellow-filled icon is displayed, as shown in the following screenshot.

In many cases, icons are clearer (they don't require reading and thinking about) and can also be smaller onscreen than text messages for indicating player status and inventory items.

When several items of the same type have been picked up, often the simplest way to convey what is being carried to the user is to display a text message showing the numeric total of each item type being carried, as shown in the following screenshot. In this recipe, the total number of stars collected is displayed using a UI Text object.

If there is a small, fixed total number of an item to be collected rather than text totals, an alternative effective UI approach is to display placeholder icons (empty or greyed out pictures) to show the user how many of the item remain to be collected, and each time an item is picked up, a placeholder icon is replaced by a full color collected icon.

In this recipe, we use grey-filled star icons as the placeholders and yellow-filled star icons to indicate each collected star, as shown in the following screenshot.

Since our UI code is getting a little more complicated, this recipe will implement the MVC design pattern to separate the view code from the core player logic (as introduced at the end of recipe Displaying single object pickups with carrying and not-carrying text).

Another approach that could be taken to show increasing numbers of images is to make use of tiled images. The same visual effect as in the previous recipe can also be achieved by making use of a tiled grey star image of width 400 (showing four copies of the grey star icon), behind a tiled yellow star image, whose width is 100 times the number of stars collected. We'll adapt the previous recipe to illustrate this technique.

When working with different kinds of pickups, one approach is to use a C# List to maintain a flexible-length data structure of the items currently in the inventory. In this recipe, we will show you how, each time an item is picked up, a new object is added to such a List collection. An iteration through the List is how the text display of items is generated each time the inventory changes. We introduce a very simple PickUp script class, demonstrating how information about a pickup can be stored in a scripted component, extracted upon collision, and stored in our List.

While the previous recipe worked fine, any old text might have been typed into the description for a pickup or perhaps mistyped (star, Sstar, starr, and so on). A much better way of restricting game properties to one of a predefined (enumerated) list of possible values is to use C# enums. As well as removing the chance of mistyping a string, it also means that we can write code to appropriately deal with the predefined set of possible values. In this recipe, we will improve our general purpose PickUp class by introducing three possible pickup types (Star, Heart, and Key), and write inventory display code that counts the number of each type of pickup being carried and displays these totals via a UI Text object on screen. We also switch from using a List to using a Dictionary, since the Dictionary data structure is designed specifically for key-value pairs...

The recipes in this chapter up to this point have been hand-crafted for each situation. While this is fine, more general and automated approaches to inventory UIs can sometimes save time and effort but still achieve visual and usability results of equal quality. In the next recipe, we will begin to explore a more engineered approach to inventory UIs by exploiting the automated sizing and layouts offered by Unity 5's Grid Layout Group component.

In this chapter, we introduced recipes demonstrating a range of C# data representations for inventory items and a range of Unity UI interface components to display the status and contents of player inventories at run time.

Inventory UI needs good quality graphical assets for a high quality result. Some sources of assets that you might wish to explore include the following sites: