The Finder gives users access to the file system. Although it’s best to minimize users’ interaction with the Finder while they’re in your app, you need to make sure your app integrates well with it.
Make sure your app bundle has the correct filename extension. The Finder looks for the
.app filename extension and treats your app appropriately when it finds it. The Finder also shows or hides the filename extension, depending on the state of the "Show all filename extensions" preference in the Advanced pane of Finder preferences.
Use an information property list to supply information to the Finder. The information property list (that is, an
Info.plist file) is the standard place to store information about your app and document types. For information on what to put in this file, see Runtime Configuration Guidelines.
Add the appropriate filename extension to documents users can create in your app. Accurate filename extensions help ensure platform interoperability. You can also set a file type and optionally a creator type for a file, although this is not strictly necessary.
Avoid changing the creator type of existing documents. The creator type implies a distinct sense of ownership over a file. Your app can assign a creator type for files it creates, but it should not change creator types for documents that are created by other apps unless the user gives explicit consent. Note that the user can still associate files with a specific app by using the Info window.
Include a Quick Look generator if your app creates documents in an uncommon or custom format. A Quick Look generator converts an uncommon format into a format that the Finder can display in Cover Flow view and in a Quick Look preview. Specifically, if your app produces documents in content types other than HTML, RTF, plain text, TIFF, PNG, JPEG, PDF, and QuickTime movies, it’s a good idea to provide a Quick Look generator so that users can view your documents they way they expect. To learn how to create a Quick Look generator, see Quick Look Programming Guide.
If necessary, report disk size or usage information appropriately. If your app needs to display this type of information, it’s important to provide values that are consistent with values reported by the Finder and other system apps, such as Activity Monitor. Otherwise, users can become confused if your app and the system report different values for the same quantity.
To ensure consistent values, be sure to calculate all disk size statistics using GB, not GiB. A GB is defined as 1,000,000,000 bytes, whereas a GiB is defined as 1,073,741,824 bytes (which is the value of 230).