[Overview][Constants][Types][Classes][Index] | Reference for unit 'fgl' (#rtl)

# TFPGMap.OnKeyCompare

Compare function for key values.

## Declaration

Source position: fgl.pp line 337

`public property TFPGMap.OnKeyCompare : TKeyCompareFunc read FOnKeyCompare write SetOnKeyCompare;`

## Description

OnKeyCompare can be set to a function that compares key values. The default value for this event is a function that compares keys based on a byte-by-byte comparison of the memory block. The function must have the following semantics:

- If the result of this function is negative, the first key (key1) is assumed to be 'less' than the second key (key2) and will be moved before the second in the list.
- If the function result is positive, the first key (key1) pointer is assumed to be 'greater than' the second key (key2)and will be moved after the second in the list.
- if the function result is zero, the keys are assumed to be 'equal' and no moving will take place.

## See also

TFPGMap.OnDataCompare |  | Compare function for data values.