With nib files, you create and manipulate your user interfaces graphically, using Xcode, instead of programmatically. Because you can see the results of your changes instantly, you can experiment with different layouts and configurations very quickly. You can also change many aspects of your user interface later without rewriting any code.
Asset catalogs help you quickly organize and manage your app's resources. In an asset catalog, each asset set represents one resource - like an image, color, or data file - that your app loads at runtime. An asset set contains one or more variations of that resource for different device characteristics, for example, platform, screen size, resolution, appearance, and language. When you refer to a resource in code, the system determines the appropriate variation to display at runtime based on the characteristics of the current device.
Documentation Describing Two Approaches
Localizing with "Make Xcode Project" - video download [54 MB]
Part 1: Passing data by value - video download [6.4 MB]
Part 2: Passing data by reference - video download [8.2 MB]
Part 3: Passing records - video download [6.9 MB]
Part 4: Basic order of operation - video download [9.4 MB]
Part 5: Function Prototypes - video download [13.8 MB]