| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |
Arguments: grid-column
Returns (or sets with setf) a function that retrieves the
value to be displayed in a grid cell. This function is called by the
default read-cell-value method, and
supplying a data-reader function and a data-object function is
an alternative to writing your own read-cell-value method. The
data-reader may
be nil
if this facility is not used. The
default value is nil
.
The data-reader
function is a property of a grid-column
, and is called once for each
grid-row that intersects that column to find the value to be displayed
in the cell at that intersection. The function should take a single
argument, which is the grid-row
's data-object. The function is typically simply
the reader function of the data-object for the attribute represented by
this grid-column
. If this
column is accessing a slot that has no writer function or the writer
function is not known, then the data-slot property could be used instead.
For example, in the employee grid example, each row represents an employee, and the Department column represents the department attribute of each employee. The data-reader function of the Department column is employee-department, which is simply the reader method for the department slot of an employee instance. To find the value to represent in the Department column for each employee, the Department column's data-reader function (employee-department) is called on the data-object (an employee) of each grid-row. The employee grid example can be found on the Examples tab of the Navigator.
NOTE: Your application typically will not call the data-reader
function, and instead will supply the data-reader function which is
then called automatically by the system as needed. Specifically, the
built-in column classes such as editable-text-column-mixin
will
call the data-reader whenever they draw a cell, and a custom draw-cell method that an
application supplies may call the default read-cell-value method, which calls
the data-reader. Otherwise the draw-cell method may use some
custom technique to find the value to draw, and a data-reader method
is not needed at all.
data-reader is a
property of the grid-column
and row-header-column
classes.
See the grid-widget
class
for an overview of writing grid-widget code.
Copyright (c) 1998-2016, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.1 page.
Created 2010.1.21.
| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |