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Chapter 4: VCL Property Arrays


Property arrays are properties like YData, SubsetLabels, and PointColors that have multiple values defined by one or two indices. These property arrays are dynamic in that they grow as you increase the indices used to set items.


Some property arrays have default elements defined and others are empty by default. Some examples of property arrays with default elements are SubsetLineTypes, SubsetPointTypes, and SubsetColors. Some examples of property arrays empty by default are RandomSubsetsToGraph, SubsetsToLegend, and MultiAxesSubsets. It is important to realize that a property array has a size and this size is often used to control image construction. If you are providing some form of custom user interface or report procedure, you may be continuously manipulating property arrays. If they grow dynamically, you also need a way to shrink or empty the property array. This can be accomplished by setting the index to (-1) or in the case of a two dimensional property array (0,-1), and equating this to the new size.


For example, RandomSubsetsToGraph is a common property array that needs to be emptied or resized. The following code shows how to empty this property array.


Integer property arrays are emptied as follows:

PEGraph1.RandomSubsetsToGraph[-1] := 0;


Two dimensional property arrays are emptied like:

PEGraph1.YData[0, -1] := 0;


String property arrays are emptied like:

PEGraph1.PointLabels[-1] := '0';


Also note that PEactions = REVERT_TO_DEFAULTS (20) which calls PEreset will empty the graph of all property settings and revert the object to its default state. This is easier and the recommended approach when you need to reset the state of the object due to repeatedly changing the object.