- Inherits from:
- EOAssociation : EODelayedObserver (EOControl) : NSObject
- EOObserving (EODelayedObserver)
An EOPopUpAssociation object displays an attribute or to-one relationship value in an NSPopUpButton (Application Kit).
|Note: This class doesn't exist in the com.apple.client.eointerface package.|
The items in the NSPopUpButton can be entered manually, or
for a relationship, constructed dynamically from values supplied
by the destination entity's EODisplayGroup. The value displayed by
the NSPopUpButton can be bound by one of three aspects:
which is useful for values representable as strings;
for integer values; and
for the destination object of a relationship.
|NSPopUpButton (Application Kit)|
|titles||An attribute of the objects in an EODisplayGroup whose values can be represented as strings.|
|selectedTitle||An attribute of the selected object whose values can be represented as strings.|
|selectedTag||An integer attribute of the selected object.|
|selectedObject||A to-one relationship of the selected object; the value
displayed is that for the attribute bound to the
|enabled||A boolean attribute of the selected object, which determines whether the NSPopUpButton is enabled.|
|Object Keys Taken|
|target||When the user chooses an item in the pop-up list, the EOPopUpAssociation updates the selected object's property with the item's title, tag, or object.|
There are several basic ways to configure a combo box and it's association. They are described below.
Selecting a String from a Static List
Suppose you have a Movie display group and you want to provide a pop-up list for setting the rating from a static list of strings. In this example, a Movie object's rating is a string property rather than a relationship to a Rating object. To do this, in Interface Builder, type the list of ratings into the pop-up list. Control-drag a connection from the pop-up list to the Movie display group. Choose EOPopUpAssociation in the Connections inspector, and bind the selectedTitle aspect to the "rating" key. With this configuration, if an object's string attribute value isn't in the pop-up list, it's temporarily added while the object is selected.
Selecting a String from a Dynamic List
This example is similar to the previous one, except in this example, a Movie object's rating is chosen from strings in a Rating database table. There's a Rating EODisplayGroup that fetches the ratings into Rating objects, and the pop-up list is filled from the "ratingString" property of the rating display group's Rating objects. To do this, in Interface Builder, control-drag a connection from the pop-up list to the Ratings display group. Choose EOPopUpAssociation in the Connections inspector, and bind the titles aspect to the "ratingString" key. Similarly, control-drag a connection from the pop-up list to the Movie display group. Again choose EOComboBoxAssociation in the Connections inspector, and bind the selectedTitle aspect to the "rating" key.
Selecting an Integer Tag from a Static List
Suppose you have a Customer enterprise object whose credit card type (Visa, MasterCard, and so on) is indicated by an integer tag. You want a user to be able to choose a customer's card type from a pop-up list. To do this, in Interface Builder, set the credit card names and tags for the pop-up list. Control-drag a connection from the pop-up list to the Customer display group. Choose EOPopUpAssociation in the Connections inspector, and bind the selectedTag aspect to the "cardType" key. You can also allow for a general "other" value by defining a special tag and setting it in the EOPopUpAssociation using setTagValueForOther. Credit card tags from the database not matching any in the pop-up list are then displayed as the "other" value. (It would also make sense to disable the pop-up list in this case, to avoid writing the meaningless tag back to the database.)
Selecting the Destination of a To-One Relationship
Suppose you have a list of employees and want to assign each
employee a department. In terms of the object model, you want to
assign a Department object as the destination of an Employee object's
To do this, in Interface Builder, control-drag a connection from
the pop-up list to a Department display group. Choose EOComboBoxAssociation
in the Connections inspector, and bind the titles aspect to the
"name" key. Similarly, control-drag a connection from the pop-up
list to the Employee display group. Again choose EOComboBoxAssociation
in the Connections inspector, and bind the selectedObject to the
"department" key. This fills the pop-up list with the names
of departments, and causes the name of the selected Employee's
Department to be selected in the pop-up list.
Creates a new EOPopUpAssociation to monitor
and update the values in aDisplayObject,
an NSPopUpList (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)
Records tag as
the "unknown" tag. When a property value doesn't match any
other tag in the pop-up list, the EOPopUpAssociation automatically
selects the item for this tag. If there's no item for this tag, the
pop-up list's selection isn't changed. This tag value is by
Returns the "unknown" tag.