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EOColumnAssociation

Inherits from:
EOAssociation : EODelayedObserver (EOControl) : NSObject

Conforms to:
NSCoding

(EOAssociation)

EOObserving (EODelayedObserver)

NSObject (NSObject)

Declared in:
EOInterface/EOColumnAssociation.h

Class Description

An EOColumnAssociation object cooperates with an EOTableViewAssociation to display values in a column of an NSTableView (Application Kit).

A column association links an NSTableColumn (Application Kit) to a single attribute of all displayed objects in an EODisplayGroup. The value of each object is displayed in its corresponding row.

Column associations provide values for the cells of each NSTableColumn, and also accept edited values to set in their display groups. The EOTableViewAssociation receives target, delegate, and data source messages from the table view, and forwards them as needed to the appropriate column association.

EOColumnAssociations provide values using NSTableView's DataSource methods tableView:setObjectValue:forTableColumn:row: and tableView:objectValueForTableColumn:. This allows values with non-string representations to be displayed. For example, if an NSImageCell (Application Kit) is used as an NSTableColumn's data cell, an EOColumnAssociation can be used to display NSImages (Application Kit) in the NSTableView.

Usable With

NSTableColumn (Application Kit)

Aspects
value	An attribute of the objects, displayed in each row of the NSTableColumn.
enabled	A boolean attribute of the objects, which determines whether each object's value cell is editable. Note that because EOTableViewAssociation also uses this aspect, you can use it with different keys to limit editability to the whole row or to an individual cell (column) in that row.

Object Keys Taken
identifier	An EOColumnAssociations sets itself as the identifier of its NSTableColumn. (Note: This key isn't formally reserved by the objectKeysTaken method, as Interface Builder doesn't treat it as an outlet.)

Example

To display the last and first names of objects in a Talent display group, in Interface Builder, Control-drag a connection from the last name column to the display group. Select EOColumnAssociation in the Connections inspector, and bind the value aspect to the "lastName" key (this automatically creates an EOTableViewAssociation to manage the individual columns). Repeat to set up a column association for the first name. Now when you run the application, the last and first names of each Talent object in the display group's displayedObjects array are put in the corresponding row.

Method Types

Sorting rows

- setSortingSelector:

- sortingSelector

Table view data source methods

- tableView:setObjectValue:forTableColumn:row:

- tableView:objectValueForTableColumn:row:

Table view delegate methods

- tableView:shouldEditTableColumn:row:

- tableView:willDisplayCell:forTableColumn:row:

Control delegate methods

- control:didFailToFormatString:errorDescription:

- control:isValidObject:

- control:textShouldBeginEditing:

Instance Methods

control:didFailToFormatString:errorDescription:

- (BOOL)control:(NSControl *)aTableView didFailToFormatString:(NSString *)aString errorDescription:(NSString *)errorDescription

Invokes shouldEndEditingForAspect:invalidInput:errorDescription: (defined by EOAssociation) and returns the result.

control:isValidObject:

- (BOOL)control:(NSControl *)aTableView isValidObject:(id)anObject

Saves the value of any cell being edited using setValue:forAspect:, and if successful sends an associationDidEndEditing: message to the receiver's EODisplayGroup. Returns YES if successful (or if no changes need be saved), NO if unsuccessful.

control:textShouldBeginEditing:

- (BOOL)control:(NSControl *)aTableView textShouldBeginEditing:(NSText *)fieldEditor

Sends an associationDidBeginEditing: message to the receiver's EODisplayGroup and returns YES.

setSortingSelector:

- (void)setSortingSelector:(SEL)aSelector

Sets the method selector used to sort rows to aSelector, one of (defined in EOControl):

EOCompareAscending
EOCompareDescending
EOCompareCaseInsensitiveAscending
EOCompareCaseInsensitiveDescending
nil (to tell the receiver not to sort)

For more information on these selectors, see the section "Comparison Methods" in the EOSortOrdering class specification (EOControl).

If the EOTableViewAssociation for the receiver's NSTableView (Application Kit) sorts its rows, it applies this method as needed to sort them. The default sorting selector is EOCompareAscending.

sortingSelector

- (SEL)sortingSelector

Returns the method selector used to sort rows, or nil if the column isn't sorted.

tableView:objectValueForTableColumn:row:

- (id)tableView:(NSTableView *)aTableView objectValueForTableColumn:(NSTableColumn *)aTableColumn row:(int)rowIndex

Returns the value of the property of the object at rowIndex bound to the value aspect.

tableView:setObjectValue:forTableColumn:row:

- (void)tableView:(NSTableView *)aTableView setObjectValue:(id)value forTableColumn:(NSTableColumn *)aTableColumn row:(int)rowIndex

Sets the property of the object at rowIndex bound to the value aspect to value.

tableView:shouldEditTableColumn:row:

- (BOOL)tableView:(NSTableView *)aTableView shouldEditTableColumn:(NSTableColumn *)aTableColumn row:(int)rowIndex

Returns NO if the enabled aspect is bound and its value for the object at rowIndex is NO. Otherwise returns YES. Note that because the enabled aspects of EOTableViewAssociation and EOColumnAssociation can be bound to different keys, you can limit editability to the whole row or to an individual cell (column) in that row.

tableView:willDisplayCell:forTableColumn:row:

- (void)tableView:(NSTableView *)aTableView willDisplayCell:(id)aCell forTableColumn:(NSTableColumn *)aTableColumn row:(int)rowIndex

Alters the display characteristics for aCell according to the values for the enabled aspect of the object at rowIndex.