data-slot

Arguments: grid-column

Returns the name of a slot that holds values to be displayed in cells of a grid-column, or else nil if this property is not being used. The value may be set at creation time by passing the data-slot initarg, or any time later by calling (setf data-slot). The default value is nil.

This property will be used when reading cell values only if the default read-cell-value method is not overridden and the grid-column has no data-reader function. It will be used when writing cell values only if the default write-cell-value method is not overriden and the grid-column has no data-writer function.

If this property is used, then when a grid cell is drawn, the value to display is found by calling slot-value with the data-object of the grid-row along with this slot name. If the user interactively edits the value in a grid cell, the new value is written back into application data by calling (setf slot-value) with the data-object of the grid-row along with this slot name and the new value.

It is usually preferable to use data-reader and data-writer functions because they will trigger the usual side effects of a slot's reader and writer functions. But data-slot can be useful for slots that do not have reader and writer functions, or when these functions are not known.

A special feature of a data-slot value is that it may indirectly access a slot of an object that's stored in a slot of the grid-row's data-object. This is done by using a value that is a list of slot names rather than a single slot name. The first slot name in the list should be a slot of the grid-row's data-object, the second slot name in the list should be a slot of the object that is found in the first slot, and so on. For example, if the data-object of each grid row is a patient object, and this grid column is editing the hospital of each patient, then the column's data-slot might be the list (hospital ceo phone-number) to access the phone number slot of the object that's in the CEO slot of the object that's in the hospital slot of the patient of each grid row. A class-grid makes use of this feature internally, but an application could use it directly as well.

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This page was not revised from the 9.0 page.
Created 2015.5.21.