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Copyright (c) 1994 by NeXT Computer, Inc. All Rights Reserved.


Inherits From: NSControl : NSView : NSResponder : NSObject

Conforms To: NSCoding (NSResponder) NSObject (NSObject)

Declared In: AppKit/NSBrowser.h

Class Description

NSBrowser provides a user interface for displaying and selecting items from a list of data, or from hierarchically organized lists of data such as directory paths. When working with a hierarchy of data, the levels are displayed in columns, which are numbered from left to right, beginning with 0. Each column consists of an NSScrollView containing an NSMatrix filled with NSBrowserCells. NSBrowser relies on a delegate to provide the data in its NSBrowserCells. See the NSBrowserCell class description for more on its implementation.

Browser Selection

An entry in an NSBrowser's column can be either a branch node (such as a directory) or a leaf node (such as a file). When the user selects a single branch node entry in a column, the NSBrowser sends itself the addColumn message, which messages its delegate to load the next column. The user's selection can be represented as a character string; if the selection is hierarchical (for example, a filename within a directory), each component of the path to the selected node is separated by /. To use some other character as the delimiter, invoke setPathSeparator:.

An NSBrowser can be set to allow selection of multiple entries in a column, or to limit selection to a single entry. When set for multiple selection, it can also be set to limit multiple selection to leaf nodes only, or to allow selection of both types of nodes together.

As a subclass of NSControl, NSBrowser has a target object and action message. Each time the user selects one or more entries in a column, the action message is sent to the target. NSBrowser also adds an action to be sent when the user double-clicks on an entry, which allows the user to select items without any action being taken, and then double-click to invoke some useful action such as opening a file.

User Interface Features

The user interface features of an NSBrowser can be changed in a number of ways. The NSBrowser may or may not have a horizontal scroller. (The NSBrowser's columns, by contrast, always have vertical scrollersalthough a scroller's buttons and knob might be invisible if the column doesn't contain many entries.) You generally shouldn't create an NSBrowser without a horizontal scroller; if you do, you must make sure the bounds rectangle of the NSBrowser is wide enough that all the columns can be displayed. An NSBrowser's columns may be bordered and titled, bordered and untitled, or unbordered and untitled. A column's title may be taken from the selected entry in the column to its left, or may be provided explicitly by the NSBrowser or its delegate.

NSBrowser's Delegate

NSBrowser requires a delegate to provide it with data to display. The delegate is responsible for providing the data and for setting each item as a branch or leaf node, enabled or disabled. It can also receive notification of events like scrolling and requests for validation of columns that may have changed.

You can implement one of two delegate types: active or passive. An active delegate creates a column's rows (that is, the NSBrowserCells) itself, while a passive one leaves that job to the NSBrowser. Normally, passive delegates are preferable, because they're easier to implement. An active delegate must implement browser:createRowsForColumn:inMatrix: to create the rows of the specified column. A passive delegate, on the other hand, must implement browser:numberOfRowsInColumn: to let the NSBrowser know how many rows to create. These two methods are mutually exclusive; you can implement one or the other, but not both. (The NSBrowser ascertains what type of delegate it has by which method the delegate responds to.)

Both types of delegate implement browser:willDisplayCell:atRow:column: to set up state (such as the cell's string value and whether the cell is a leaf or a branch) before an individual cell is displayed. (This delegate method doesn't need to invoke NSBrowserCell's setLoaded: method, because the NSBrowser can determine that state by itself.) An active delegate can instead set all the cells' state at the time the cells are created, in which case it doesn't need to implement browser:willDisplayCell:atRow:column:. However, a passive delegate must always implement this method.

Setting the Delegate

Target and Action

- (SEL)doubleAction Returns the NSBrowser's double-click action method.

- (BOOL)sendAction Sends the action message to the target. Returns YES upon success, NO if no responder for the message could be found.

- (void)setDoubleAction:(SEL)aSelector Sets the NSBrowser's double-click action to aSelector.

Setting Component Classes

Setting NSBrowser Behavior

Allowing Different Types of Selection

Setting Arrow Key Behavior

Showing a Horizontal Scroller

Setting the NSBrowser's Appearance

Manipulating Columns

Manipulating Column Titles

Scrolling an NSBrowser

Event Handling

Getting Matrices and Cells

Getting Column Frames

Manipulating Paths

Arranging an NSBrowser's Components

Methods Implemented by the Delegate