How do I convert an integer to an enumerated type?

问题:

I know how to convert an enumerated type to an integer.

type
  TMyType = (mtFirst, mtSecond, mtThird); 

var 
  ordValue:integer;
  enumValue:TMyType;
...
ordValue:= Ord(mtSecond); // result is 1

But how do I do the inverse operation and convert an integer to an enumerated type?

回答1:

As Ken answered, you just cast it. But to make sure you have correct value you can use code like:

if (ordValue >= Ord(Low(TMyType))) and (ordValue <= Ord(High(TMyType))) then
    enunValue := TMyType(ordValue)
else 
    raise Exception.Create('ordValue out of TMyType range');

回答2:

You can cast the integer by typecasting it to the enumerated type:

ordValue := Ord(mtSecond);
enumValue := TMyType(ordValue);

回答3:

Take care with casting because it requires full mapping with your ordinal type and integers. For example:

type Size = (Small = 2, Medium = 3, Huge = 10);
var sz: Size;
...
sz := Size(3); //means sz=Medium
sz := Size(7); //7 is in range but gives sz=outbound