Let me jump in here and say that I agree that strings are useful. IMO any scalar type should be allowed for enum's. String enum's are great for understanding debug data. Also it would integrate smoothly with MySQL enums (building queries) and when you want to model enumerations in an external API or framework. When you say "enums should be integers" you assume that the programmer has the final decision on the values. But if you want to enumerate possible string return codes from an external API you'd be forced to write a translation function that translate the values you read to the internal enumeration representation.
For example, say that http://www.example.org/api can return either "fail", "success" or "timeout", you'd like to put these in an enumeration so they make sense instead of having magic values scattered across the code. enum ExampleReturnCodes { FAILURE = "fail"; SUCCESS = "success"; TIMEOUT = "timeout"; } if ($ret == ExampleReturnCodes::FAILURE) echo "noes"; This also highlights why it would be nice to name enumerations just like classes. They provide a handle for the constants within so they can be used for reflection. See, I'd like to do something like: if ($ret enumof ExampleReturnCodes) \trigger_error("Unknown enumeration value returned!", \E_USER_ERROR); and: print("Got: " . ExampleReturnCodes::getName($ret)); // PrintsGot: FAILURE I'm suggesting this as an additional behavior. Declaring enumerations without names should make the contents be declared just as normal namespace/class constants. In addition, declaring a named enumeration "enum_name" in a class could give the enumeration the name either "enum_name" (if it wouldn't be confusing and the named collision risk is acceptable), "class_name::enum_name" (if the :: operator could be programmed to also resolved enumeration types and not only class constants), "class_name_enum_name" (if it would be acceptable to automatically merge the class name with the enumeration name) (and possibly other solutions). Another solution is to forbid class enumerations from being named and only use them as a constant grouping syntax. My 5 cents. Hannes On 18 February 2011 15:44, Arvids Godjuks <arvids.godj...@gmail.com> wrote: > Hello! > > I should comment on why people want strings as enum values - just look > at ENUM type in MySQL. People use it, and if you take a look from that > perspective - it makes sense. > > But we are not a MySQL only world, so it does not make sense to do > strings, because in other databases usually 1 byte integers are used > for that. > > > P.S. But I really like MySQL ENUM, it's really helpfull to see some > meaningfull representation instead of plain numbers. And MySQL is able > to convert enum to real integer like it is stored internaly: SELECT > enum + 0 AS enum FROM table. Will get you the numbers, not the string > representations. So it's really no brainer to make enumerations to > work transparently with MySQL. > > 2011/2/18 Jarrod Nettles <jnett...@inccrra.org>: >> I did some research on methods in enums and discovered that there is some >> usefulness to the idea - I wouldn't go so far as to say that they would be >> needed, but C#, for example, allows you to create extension methods for >> enums and MSDN has a decent real-world example of its use. >> >> http://msdn.microsoft.com/en-us/library/bb383974.aspx >> >> I still don't understand why we would need string values (or any other >> non-integral type) but like you said Ben - if you need something like that >> you're not using the right datatype. Build a class. Here's my reasoning for >> enum values. >> >> enum Wood{ >> OAK, >> ASH, >> WILLOW, >> GOPHER >> } >> >> There's nothing in there that would necessitate needing a string value and >> really, if you need a string value, pass in a string as your parameter! >> Enumerations should be used to represent a set of data where the value >> itself isn't so important, it’s the consistency of the value that's >> important. It’s the fact that I've chosen gopher wood and I know that even >> though Wood::GOPHER really means "3", I don't have to remember what "3" >> represents because I can specifically type that I want gopher. >> >> >> -----Original Message----- >> From: Ben Schmidt [mailto:mail_ben_schm...@yahoo.com.au] >> Sent: Thursday, February 17, 2011 4:52 PM >> To: Martin Scotta >> Cc: Jarrod Nettles; Thomas Gutbier; internals@lists.php.net >> Subject: Re: [PHP-DEV] Re: Clarification on the Enum language structure >> >>>> Also, I feel like it should be restricted to integral types only, and >>>> defaults to a zero-based incrementing integer. This is more in line with >>>> other programming languages that already implement enums and will present >>>> "expected behavior" for people moving over to PHP. >>>> >>> for me that's a plain old interpretation of constants. >>> constant values were only integer values because of their implementation, >>> nowadays they could be anything you want, int, float, string and even >>> objects. >> >> I partially agree with that. >> >> I'm going to be a bit extreme here, but here's a thought: >> >> An enum is something you use conceptually for a set of constant values >> which aren't related in a numerical or other fashion (where another type >> would make more sense). In an enum, the only meaning of a constant is >> the meaning expressed in that constant's name. >> >> So you shouldn't want to use ints, floats, strings, certainly not >> objects, for enum values. If you feel yourself wanting to do this, an >> enum is not the right datatype for your purpose--you should be using one >> of those other types instead, possibly with a very few defined constants >> for commonly-used or 'magic' values. >> >> The issue, then, of what type underlies an enum is mostly to do with >> internal implementation, and more importantly, serialisation. Integers >> are the simplest and most obvious way to do this. But short strings, >> particularly string representations of the enum's symbols, could be a >> nice way to make serialised data more readable, and less fragile (e.g. >> if values are added to the enum, the mapping of strings to previous >> constants does not change, no matter where the new value is added). >> >> I see no reason to use floats or objects (or resources, or arrays, or >> ...). >> >> Ben. >> >> >> >> <html> >> <body> >> Jarrod Nettles Application Developer - Technology INCCRRA p 309.829.5327 - f >> 309.828.1808 This e-mail message may contain privileged or confidential >> information. If you are not the intended recipient, you may not disclose, >> use, disseminate, distribute, copy >> or rely upon this message or attachment in any way. If you received this >> e-mail message in error, please return by forwarding the message and its >> attachments to the sender. INCCRRA does not accept liability for any errors, >> omissions, corruption or virus in >> the contents of this message or any attachments that arises as a result of >> e-mail transmission. Please consider your environmental responsibility >> before printing this e-mail >> </body> >> </html> >> >> -- >> PHP Internals - PHP Runtime Development Mailing List >> To unsubscribe, visit: http://www.php.net/unsub.php >> >> > > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: http://www.php.net/unsub.php > > -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
