available-reader

Arguments: grid-column

Returns a function that returns whether each of the grid cells in a particular column of a grid-widget is currently accessible to the user, or else returns nil to determine the availability in other ways (see cell-available). The default value is nil.

The available-reader function is a property of a particular grid-column, and is called once for each grid-row that intersects that column to determine the availability of the cell at the intersection of that row and column. The function should take one argument, which is the data-object of a grid-row. If the attribute represented by the grid-column should currently be accessible to the user for the data-object that is passed to the function, then the function should return true, and otherwise it should return nil. When not available, a grid-cell appears grayed out and its value may not be modified by the user.

This property value may be specified as either a function name symbol (which would be more debuggable), or a function object (which may be slightly faster, though probably insignificantly), or nil.

Example: In the employee grid example, each grid-row represents an employee. If the "Full Time?" grid-column had an available-reader function, then the system would periodically pass an employee to that function, and the function should return true if the "Full Time?" cell for that employee should currently be accessible to the user. The employee grid example can be found on the Examples tab of the Navigator.

NOTE: An application does not call the available-reader function; it supplies the available-reader function by calling (setf available-reader) or by passing the :available-reader initarg when calling make-instance to create a grid-column. The specified function is then called automatically by the system as needed.

available-reader is a property of the grid-column and row-header-column.

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This page was not revised from the 10.0 page.
Created 2019.8.20.