Generics equality and comparing in Delphi
Suppose you have 2 values that are declared as generics, and you want to perform equality, or comparison, how would you do this?
Value1, Value2: V;
You'll need to obtain a generics comparer.
Given the declaration: LComparer: IComparer<V>;
// Here's how you obtain a comparer:
LComparer := TComparer<V>.Default; // declared in System.Generics.Defaults;
Then, to compare, here's what you do:
case LComparer.Compare(Value1, Value2) of
-1: ... Value1 is smaller than Value2
0: ... Value1 is equal to Value2
1: ... Value1 is greater than Value2
In cases of LComparer being assigned the result of TComparer<string>.Default, you can get values less than and greater than 0, so you might want to consider another way to compare, like so:
LCompareResult := LComparer.Compare(Value1, Value2) ;
if LCompareResult < 0 then
if LCompareResult = 0 then
if LCompareResult > 0 then
Thanks to fellow MVP, Stefan G who pointed out that for string comparers, you can get results having negative and positive values, not just -1 and +1.