PATH  WebObjects 4.0 Documentation > EOInterface Reference



EOColumnAssociation

Inherits From:
EOAssociation : EODelayedObserver (EOControl) : NSObject

EOObserving (EODelayedObserver)

Inherits From:
com.apple.yellow.eointerface (Yellow Box)


Class Description

An EOColumnAssociation object cooperates with an EOTableViewAssociation to display values in a column of an NSTableView (Application Kit). It is for use in Yellow Box applications only. For an equivalent Java Client class, see the EOTableColumnAssociation class specification.

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.

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

EOColumnAssociations provide values using NSTableView's DataSource methods


tableViewSetObjectValueForLocation and
tableViewObjectValueForLocation . 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 identifer 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 correponding row.


Method Types

Sorting rows
setSortingSelector
sortingSelector
Table view data source methods
tableViewSetObjectValueForLocation
tableViewObjectValueForLocation
Table view delegate methods
tableViewShouldEditLocation
tableViewWillDisplayCell
Control delegate methods
controlDidFailToFormatStringErrorDescription
controlIsValidObject
controlTextShouldBeginEditing

Constructors

public EOColumnAssociation(java.lang.Object aDisplayObject)

Creates a new EOColumnAssociation to monitor and update the row values in aDisplayObject, an NSTableColumn (Application Kit).

You normally set up associations with the Interface Builder application, in which case you don't need to create them programmatically. However, if you do create them up programmatically, setting them up is a multi-step process. After creating an association, you must bind its aspects and establish its connections.

See also: bindAspect (EOAssociation), establishConnection (EOAssociation)


Instance Methods


setSortingSelector

public void setSortingSelector(com.apple.yellow.foundation.NSSelector aSelector)

Sets the method selector used to sort rows to aSelector, one of:

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 EOSortOrdering.EO_COMPARE_ASCENDING.


sortingSelector

public com.apple.yellow.foundation.NSSelector sortingSelector()

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

Data Source and Delegate Methods

These methods are forwarded by the corresponding NSTableView's EOTableViewAssociation to the appropriate EOColumnAssociation.


controlDidFailToFormatStringErrorDescription

public boolean controlDidFailToFormatStringErrorDescription(
com.apple.yellow.application.NSControl aTableView,
java.lang.String aString,
java.lang.String errorDescription)

Invokes shouldEndEditing (defined by EOAssociation) and returns the result.


controlIsValidObject

public boolean controlIsValidObject(
com.apple.yellow.application.NSControl aNSControl,
java.lang.Object anObject)

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


controlTextShouldBeginEditing

public boolean controlTextShouldBeginEditing(
com.apple.yellow.application.NSControl aNSControl,
com.apple.yellow.application.NSText aNSText)

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


tableViewObjectValueForLocation

public java.lang.Object tableViewObjectValueForLocation(
com.apple.yellow.application.NSTableView aNSTableView,
com.apple.yellow.application.NSTableColumn aNSTableColumn,
int anInt)

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


tableViewSetObjectValueForLocation

public void tableViewSetObjectValueForLocation(
com.apple.yellow.application.NSTableView aTableView,
java.lang.Object value,
com.apple.yellow.application.NSTableColumn aTableColumn,
int rowIndex)

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


tableViewShouldEditLocation

public boolean tableViewShouldEditLocation(
com.apple.yellow.application.NSTableView aTableView,
com.apple.yellow.application.NSTableColumn aTableColumn,
int rowIndex)

Returns false if the enabled aspect is bound and its value for the object at rowIndex is false. Otherwise returns true. 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.


tableViewWillDisplayCell

public void tableViewWillDisplayCell(
com.apple.yellow.application.NSTableView aTableView,
java.lang.Object aCell,
com.apple.yellow.application.NSTableColumn aTableColumn,
int rowIndex)

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





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