Is it possible to cast/convert an Enumeration Value to an Integer in the Delphi Programming Language?
If yes, then how?
4 Answers
This is called out explicitly at the documentation for enumerated types:
Several predefined functions operate on ordinal values and type identifiers. The most important of them are summarized below.
| Function | Parameter | Return value | Remarks |
|---|---|---|---|
| Ord | Ordinal expression | Ordinality of expression's value | Does not take Int64 arguments. |
| Pred | Ordinal expression | Predecessor of expression's value | |
| Succ | Ordinal expression | Successor of expression's value | |
| High | Ordinal type identifier or variable of ordinal type | Highest value in type | Also operates on short-string types and arrays. |
| Low | Ordinal type identifier or variable of ordinal type | Lowest value in type | Also operates on short-string types and arrays. |
answered Mar 29, 2017 at 10:55
David Heffernan
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5 Comments
Delmo
Then... which could be the best practice
Ord(SomeEnumVariable) or Integer(SomeEnumVariable) ?David Heffernan
@Delmo Use
Ord and so avoid a cast.Delmo
Thanks @David but what is the cons of using a typecast?
David Heffernan
@Delmo As a rule, one should avoid typecasting because it breaks type safety. In this case it is safe enough. Why do you not like using
Ord?Delmo
I like what the best practice claim ;) I just wanna know if there was a preferred way over other. Thanks again!
I see David has posted you a good answer while I was writing this, but I'll post it anyway:
program enums; {$APPTYPE CONSOLE} uses SysUtils, typinfo; type TMyEnum = (One, Two, Three); var MyEnum : TMyEnum; begin MyEnum := Two; writeln(Ord(MyEnum)); // writes 1, because first element in enumeration is numbered zero MyEnum := TMyEnum(2); // Use TMyEnum as if it were a function Writeln (GetEnumName(TypeInfo(TMyEnum), Ord(MyEnum))); // Use RTTI to return the enum value's name readln; end. 
4 Comments
user30478
You have done a great job posting this 'anyway' because other experts don't have an inkling how easy it is to confuse what an Enum variable speaks about. There's the doc of course but many reasons to skip it. "One example saves a ton of theory".
user30478
I have already up-voted this long ago, but somehow needed to see it again. Thanks for the reply.
Michael Riley - AKA Gunny
@MartynA I love your succinct explanation on uses of RTTI. Please consider writing a Delphi blog.
MartynA
@MichaelRiley-AKAGunny: That's very kind. Actually, prompted by an earlier comment of yours and one from Dave Nottage, I'm thinking seriously about it. In fact, the past few days I've been working on a ToolsApi project that might be interesting enough to be worth blogging about. Watch this space, as they say.
Casting the enum to an integer works. I could not comment on the other answers so posting this as an answer. Casting to an integer may be a bad idea (please comment if it is).
type TMyEnum = (zero, one, two); var i: integer; begin i := integer(two); // convert enum item to integer showmessage(inttostr(i)); // prints 2 end; Which may be similar to Ord(), but I am unsure which is the best practice. The above also works if you cast the enum to an integer
type TMyEnum = (zero, one, two); var MyEnum: TMyEnum; i: integer; begin MyEnum := two; i := integer(MyEnum); // convert enum to integer showmessage(inttostr(i)); // prints 2 end; 
3 Comments
Sertac Akyuz
Compare
ShowMessage(IntToStr(High(Ord(two)))) with ShowMessage(IntToStr(High(Integer(two)))).
Another Prog
Is the Ord() function a leftover from turbopascal days that people are using when there were no casts available? Would be interesting to know the reasons for when and when not to use a cast vs Ord().... AFAIR at one point the pascal language had no casting ability and special functions were used instead, but I'm not old enough to remember or know for certain :-)
Delmo
@AnotherProg, about the best practice between
Ord(MyEnum) and Integer(MyEnum), I made an explicit question to @David. Pls see the comments of the David's answer.You can use the Ord() function for this. For clarity, it may be better to write a pair of IntToEnum() and EnumToInt() functions though.
Ord(myEnumValue).