Pasteboard

A pasteboard is a secure and standardized mechanism for the exchange of data within or between applications. Many operations depend on the pasteboard, notably copy-cut-paste. On OS X, drag-and-drop operations and application services also depend upon the pasteboard. You can also use pasteboards in other situations where sharing data between applications is desirable.

A pasteboard in the AppKit framework is represented by an instance of the NSPasteboard class; the equivalent class in the UIKit framework is UIPasteboard. Pasteboard objects access a shared repository where a writer object and a reader object meet to exchange data. The writer, also known as the pasteboard owner, deposits data on a pasteboard instance and moves on. The reader accesses the pasteboard, asynchronously, and copies the data into its address space.

Pasteboards can be public or private to one or more applications. Public pasteboards are system provided and are available to all applications. All pasteboards, public and private, must have a unique name. Both platforms have general-purpose pasteboards and pasteboards used in search operations. In iOS, these pasteboards are named UIPasteboardNameGeneral and UIPasteboardNameFind; in OS X, they are named NSGeneralPboard and NSFindPboard. OS X has additional named system pasteboards for rulers, fonts, and drag-and-drop operations. An application on either platform typically uses one of the system pasteboards, but may create a private pasteboard under a unique name; for example, it might create a private pasteboard to share data with a sibling application that was created by the same software vendor.

A Pasteboard Holds Multiple Items in Multiple Representations

A pasteboard item is a piece of data placed onto a pasteboard. A pasteboard can hold a single item, such as an image file or a document, or it can hold multiple items. Methods of the pasteboard classes (and, on OS X, the NSPasteboardItem class) enable you to write and read single or multiple pasteboard items either as property-list objects or as binary data.

To facilitate sharing between applications with different capabilities, a pasteboard item can include multiple representations of the same data. For example, a rich-text editor might provide RTFD, RTF, and plain-text representations of the data it writes as a pasteboard item. Each representation of an item is identified by a different Uniform Type Identifier (UTI).