Delphi Check variable value in Type Declaration
-
28-09-2019 - |
Question
How can I determine if the value of a variable is within the range of a Type Declaration. Ex.
Type
TManagerType = (mtBMGR, mtAMGR, mtHOOT);
...
var
ManagerType: TManagerType;
....
procedure DoSomething;
begin
if (ManagerType in TManagerType) then
DoSomething
else
DisplayErrorMessage;
end;
Thanks, Pieter.
Solution
InRange: Boolean;
ManagerType: TManagerType;
...
InRange := ManagerType in [Low(TManagerType)..High(TManagerType)];
As Nickolay O. noted - whilst boolean expression above directly corresponds to:
(Low(TManagerType) <= ManagerType) and (ManagerType <= High(TManagerType))
compiler does not perform optimization on checking membership against immediate set based on single subrange. So, [maturely] optimized code will be less elegant.
OTHER TIPS
Well, a variable of type TManagerType has to be in that range since that's how Pascal enumerated types work. The only way it could not be is if you have done something naughty behind the compiler's back.
Another way to write this would be:
InRange(ord(ManagerType), ord(low(ManagerType)), ord(high(ManagerType)))
You should check this via: if mType > High(TManagerType) then ...
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