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Property :: previous - Try selecting previous instance in collection

The function locates and reads the previous instance in a collection starting from the currently located one. When no instance is located, the function selects the last valid instance.

When a filter has been defined for the collection, the function returns the previous valid instance according to the filter condition.

The function returns true, when previous instance has been located successfully. Otherwise it returns false. In case of read errors or when the property handle is not accessible the function throws an exception.
Notes:

Since error handling in previous() loops becomes difficult, a better way of iterating through a collection is often using get(iPosition) or getRelative(iPosition)and count() or relativeCount() in order to determin the size of collection.

Return value:  Success ( bool  )

The value is true when the function was executed successfully. Otherwise the value is set to false.

Implementation overview

Implementation details

  1. Locate previous instance
    bool Property  :: previous (  )

    The function locates the previous instance in the property handle without reading it. The instance might be selected when a filter has been set for the property handle.

    In order to make sure that the instance is selected, one may call get() or previous(true).
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  2. Locate previous instance for key level
    bool Property  :: previous ( int32 iKeyLevel, bool bRead )

    The switch level (iKeyLevel) allows defining the last key components that must alter. This allows e.g. providing all instances without duplicate key values, when fixing the last key component.
    • iKeyLevel - Number of fixed key component

      The switch level defines the key component number that need not change when calling next() or locateKey() beginning with 1 for the first key component.
    • bRead - Read option

      The option forces the function to read the instance when it could be located.
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  3. Locate and read previous instance
    bool Property  :: previous ( bool bRead )

    The function locates and reads the previous instance, when passing true in bRead. When passing false, the function tries to locate the instance without reading.
    • bRead - Read option

      The option forces the function to read the instance when it could be located.
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