The cell is associated with IconCollectionViewCell. In the IconCollectionViewController. What we are going to do is to fill the collection view with images and create a grid UI using diffable data source. The figure below shows the final deliverable.
To use the UICollectionDiffableDataSource object, we need to specify the number of sections and the cell configuration of each section. For this demo app, we only have a single section. We use enum to define a new Section type. In the enumeration, it only has one case because the table has a single section.
I name the case all , which means all records. But you can actually name it to whatever name you like. We will write a new function called configureDataSource for this purpose. Insert the following code in the class:. This closure is referred as the cell provider. UICollectionViewDiffableDataSource is a generic object which is capable to handle different types of section and item of a collection view. The type Section and Icon inside the angle bracket indicated that we use the Section type for the section.
Since we are going to display the data stored in iconSet , the Icon type is used for the cell data. Icon is required to conform the Hashable protocol. Switch over to Icon. Now that we have created the function for configuring the data source, declare the following variable in IconCollectionViewController to use it:. Furthermore, we need to connect this data source with the collection view.
Insert the following code in the viewDidLoad method:. You may wonder why we add a modifier lazy before the variable declaration. If you try to omit the lazy keyword, Xcode will show you the following message:. In this case, you must declare the variable with the lazy modifier because its initial value cannot be retrieved until after the instance initialization completes.
All raywenderlich. Start by downloading the project materials using the Download Materials button at the top or bottom of this tutorial. The project, fittingly called RayTube, allows you to browse a collection of RayWenderlich video courses, search for a specific one, and tap it to view more details about it. Tap a video to see its details.
Also, try searching for a specific video by title using the search bar. This UI looks like it stutters, which may not be the animation you want. You need to that smooth animation! While adding a diffable data source, you will automagically solve this issue as well.
This protocol tells the collection view what cell to display, how many cells to display, which section to display the cells in, and so on. Rather than telling the data source how many items to display, you tell it what sections and items to display. This will in turn cause the collection view to animate the changes, such as updates, insertions and deletions. Smart, right!? More on this next. To create your section type, add the following code below videoList in VideosViewController.
To keep things concise, create a type alias for the data source. This mitigates the need to write UICollectionViewDiffableDataSource value types when you need to configure the data source as well as every time you need to reference the same data type. Below the section type, write the following code to declare a DataSource type alias:.
Hashable allows the diffable data source to perform updates when videos are added, removed or updated. Conformance to the protocol is needed in order to know whether or not two elements are equal to each other. Next, you need to implement the protocol methods. Add the following code below init title:thumbnail:lessonCount:link: :. Open VideosViewController. Now that Video conforms to Hashable , you can finish creating the diffable data source.
Specifically, delete the following two methods:. You can delete these methods because the diffable data source automatically handles these functionalities for you. This creates the data source for the collection view. You must mark it lazy because Swift requires VidoesViewController to complete initialization before you can call makeDataSource. This ensures the app retrieves videos directly from the dataSource. This is important because UICollectionViewDiffableDataSource might do work in the background that makes videoList inconsistent with the currently displayed data.
This is where snapshots come in! NSDiffableDataSourceSnapshot stores your sections and items, which the diffable data source references to understand how many sections and cells to display. It works! But there is a small problem. Instead of reloading the entire collection view, you new apply a new snapshot to the database, which will cause the changes to animate. You can add another case to the enum to implement multiple sections.
For example, a messaging app with a friends section and an others section. Option Two The second option is to change Section from a value type to a class. Afterward, you can freely create any number of these objects without having to predefine each section. This option is great if you have a server that provides categories that can change at any time, or if you allow users to create sections dynamically.
Next, you need to create some sections. Open Video. This array stores all the videos the app displays. This will cause an issue in the places where you use Video. Phew, lots of code. Here you created a static property allSections which has four sections with one or more videos each. This is basically just dummy data — in a fully fledged application you would fetch this information from a server. Next, you need to update applySnapshot animatingDifferences: to work with Section.
There are two changes here. First, you append the sections array to the snapshot. Second, you loop over each section and add its items videos to the snapshot. Now that you have sections in the app, you need to fix the search feature again. This is the last time, I promise. The previous method that processed a search query returned an array of videos, so you need to write a new method that returns an array of sections.
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A diffable data source object is. A diffable data source object is a specialized type of data source that works together with your collection view object. It provides the behavior you need. Creating a Diffable Data Source UICollectionViewDiffableDataSource has two generic types: Section type and item type. If you've used.