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  • What are the downsides of implementing a singleton with Java's enum?

    - by irreputable
    Traditionally, a singleton is usually implemented as public class Foo1 { private static final Foo1 INSTANCE = new Foo1(); public static Foo1 getInstance(){ return INSTANCE; } private Foo1(){} public void doo(){ ... } } With Java's enum, we can implement a singleton as public enum Foo2 { INSTANCE; public void doo(){ ... } } As awesome as the 2nd version is, are there any downsides to it? (I gave it some thoughts and I'll answer my own question; hopefully you have better answers)

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  • JSON serialization of c# enum as string

    - by ob
    I have a class that contains an enum property, and upon serializing the object using JavaScriptSerializer, my json result contains the integer value of the enumeration rather than its string "name". Is there a way to get the enum as a string in my json without having to create a custom JavaScriptConverter? Perhaps there's an attribute that I could decorate the enum definition, or object property, with? As an example: enum Gender { Male, Female } class Person { int Age { get; set; } Gender Gender { get; set; } } desired json result: { "Age": 35, "Gender": "Male" }

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  • Logic inside an enum

    - by Vivin Paliath
    My colleagues and I were having a discussion regarding logic in enums. My personal preference is to not have any sort of logic in Java enums (although Java provides the ability to do that). The discussion in this cased centered around having a convenience method inside the enum that returned a map: public enum PackageTypes { Letter("01", "Letter"), .. .. Tube("02", "Packaging Tube"); private String packageCode; private String packageDescription; .. .. public static Map<String, String> toMap() { Map<String, String> map = new LinkedHashMap<String, String>(); for(PackageType packageType : PackageType.values()) { map.put(packageType.getPackageCode(), packageType.getPackageDescription()); } return map; } } My personal preference is to pull this out into a service. The argument for having the method inside the enum centered around convenience. The idea was that you don't have to go to a service to get it, but can query the enum directly. My argument centered around separation of concern and abstracting any kind of logic out to a service. I didn't think "convenience" was a strong argument to put this method inside an enum. From a best-practices perspective, which one is better? Or does it simply come down to a matter of personal preference and code style?

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  • Iterate over enum?

    - by Rosarch
    I'm trying to iterate over an enum, and call a method using each of its values as a parameter. There has to be a better way to do it than what I have now: foreach (string gameObjectType in Enum.GetNames(typeof(GameObjectType))) { GameObjectType kind = (GameObjectType) Enum.Parse(typeof (GameObjectType), gameObjectType); IDictionary<string, string> gameObjectData = PersistentUtils.LoadGameObject(kind, persistentState); } //... public static IDictionary<string, string> LoadGameObject(GameObjectType gameObjectType, IPersistentState persistentState) { /* ... */ } Getting the enum names as strings, then parsing them back to enums, feels hideous.

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  • Enum values doubts?

    - by maddy
    Hi all, Is there any possible way to do any arithmetic operations on enum values enum Type{Zero=0,One,Two,Three,Four,Five,Six,Seven,Eight,Nine}; main() { enum Type Var = Zero; for(int i=0;i<10;i++) { switch(Var) { case Zero: /*do something*/ case One: /*Do something*/ ..... } Var++;(I know that this increment is not possible,But is there anyway by which we can have this variable named Var increment. regards maddy

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  • Enum as a Parameter in Dynamics AX

    - by Lauren
    My report has a parameter which uses a base enum. The enum has 4 different options to choose when running the report. How do I insert an option which uses all 4 at once? For example, I have an enum named Phone and it has 4 types: 1 = None, 2 = Home, 3 = Mobile, 4 = Work. In a drop down, how do I add option 5 = None+Home+Mobile+Work? Thank you!

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  • C++ enum in foreach

    - by Spencer
    I've have a card class for a blackjack game with the following enums: enum Rank { Ace, Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten, Jack, Queen, King }; enum Suit { Clubs, Diamonds, Hearts, Spades }; When I create the deck I want to write the code like this: // foreach Suit in Card::Suit // foreach Rank in Card::Rank // add new card(rank, suit) to deck I believe there is no foreach in c++. However, how do I traverse an enum? Thanks, Spencer

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  • Enum "copy" problem

    - by f0b0s
    Hi all! I have a class, let's call it A. It has a enum (E) and a method Foo(E e), with gets E in the arguments. I want to write a wrapper (decorator) W for A. So it'll have its own method Foo(A::E). But I want to have some kind of encapsulation, so this method should defined as Foo(F f), where F is another enum defined in W, that can be converted to A::E. For example: class A { public: enum E { ONE, TWO, THREE }; void Foo(E e); }; class B { //enum F; // ??? void Foo(F f) { a_.Foo(f); } private: A a_; }; How F should be defined? I don't want to copy value like this: enum F { ONE = A::ONE, TWO = A::TWO, THREE = A::THREE }; because its a potential error in the near feature. Is the typedef definition: typedef A::E F; is the best decision? Is it legal?

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  • Assigning an @Annotation enum a value

    - by h2g2java
    I created enum Restrictions{ none, enumeration, fractionDigits, length, maxExclusive, maxInclusive, maxLength, minExclusive, minInclusive, minLength, pattern, totalDigits, whiteSpace; public Restrictions setValue(int value){ this.value = value; return this; } public int value; } So that I could happily do something like this, which is perfectly legal syntax. Restrictions r1 = Restrictions.maxLength.setValue(64); The reason being is, I am using enum to restrict the type of restriction that could be used, and be able to assign a value to that restriction. However, my actual motivation is to use that restriction in an @annotation. @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD}) public @interface Presentable { Restrictions[] restrictions() default Restrictions.none; } So that, I intended to do this: @Presentable(restrictions=Restrictions.maxLength.setValue(64)) public String userName; to which, the compiler croaks The value for annotation enum attribute must be an enum constant expression. Is there a way to accomplish what I wish to accomplish

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  • How do I implement this public accesible enum

    - by Psytronic
    Hey guys, I'm trying to access my class's private enum. But I don't understand the difference needed to get it working compared to other members; If this works: private double dblDbl = 2; //misc code public double getDblDbl{ get{ return dblDbl; } } Why can I not do it with enum? private enum myEnum{ Alpha, Beta}; //misc code public Enum getMyEnum{ get{ return myEnum; } } //throws "Window1.myEnum" is a "type" but is used like a variable

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  • How to declare strings in enum in C

    - by Sridevi
    Hello, typedef enum testCaseId { "TC-HIW-0019" = 0, "TC-HIW-0020", "TC-HIW-0021" } testCaseId; I need my test cases to be represented in enum. In my test function, I need to switch between the test cases like: void testfunc(uint8_t no) { switch(no) { case 0: case 1: default: } } So can anyone help on how to use enum to declare strings.

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  • Using enum values to represent binary operators (or functions)

    - by Bears will eat you
    I'm looking for an elegant way to use values in a Java enum to represent operations or functions. My guess is, since this is Java, there just isn't going to be a nice way to do it, but here goes anyway. My enum looks something like this: public enum Operator { LT, LTEQ, EQEQ, GT, GTEQ, NEQ; ... } where LT means < (less than), LTEQ means <= (less than or equal to), etc - you get the idea. Now I want to actually use these enum values to apply an operator. I know I could do this just using a whole bunch of if-statements, but that's the ugly, OO way, e.g.: int a = ..., b = ...; Operator foo = ...; // one of the enum values if (foo == Operator.LT) { return a < b; } else if (foo == Operator.LTEQ) { return a <= b; } else if ... // etc What I'd like to be able to do is cut out this structure and use some sort of first-class function or even polymorphism, but I'm not really sure how. Something like: int a = ..., b = ...; Operator foo = ...; return foo.apply(a, b); or even int a = ..., b = ...; Operator foo = ...; return a foo.convertToOperator() b; But as far as I've seen, I don't think it's possible to return an operator or function (at least, not without using some 3rd-party library). Any suggestions?

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  • difference between #define and enum{} in C

    - by guest
    when should one use enum {BUFFER = 1234}; over #define BUFFER 1234 ? what are the advantages enum brings compared to #define? i know, that #define is just simple text substitution and enum names the constant somehow. but why would one need that at all?

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  • Objective-C : enum like Java (int values and many others for each enum)

    - by Oliver
    In Java, you can make an enum having multiples values. In objective-C, this cannot be done easily. I've read many pages about this but I didn't found anything satisfying that would allow me to use enums by a simple way and to keep the enum declaration and their different values in the same file. I would like to write something like this in a enums.h : // ======================================== typedef enum {eRED, eGREEN, eBLUE} ColorEnum; int colorValues[] = { 0xFF0000, 0x00FF00, 0x0000FF }; NSArray *colorNames = [NSArray arrayWithObjects:@"Red color", @"light green", @"Deep blue", nil]; // ======================================== and be able to use thoses global variables to manage my stuff anywhere like : int color = colorValues[eRED]; But I don't know how to write this. I have compile errors like "ColorValues" is defines many times. Or if I just use "static", I have many "ColorValues" not used in .m file... Could you help me ?

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  • What is the best way to send structs containing enum values via sockets in C.

    - by Axel
    I've lots of different structs containing enum members that I have to transmit via TCP/IP. While the communication endpoints are on different operating systems (Windows XP and Linux) meaning different compilers (gcc 4.x.x and MSVC 2008) both program parts share the same header files with type declarations. For performance reasons, the structures should be transmitted directly (see code sample below) without expensively serializing or streaming the members inside. So the question is how to ensure that both compilers use the same internal memory representation for the enumeration members (i.e. both use 32-bit unsigned integers). Or if there is a better way to solve this problem... //type and enum declaration typedef enum { A = 1, B = 2, C = 3 } eParameter; typedef enum { READY = 400, RUNNING = 401, BLOCKED = 402 FINISHED = 403 } eState; #pragma pack(push,1) typedef struct { eParameter mParameter; eState mState; int32_t miSomeValue; uint8_t miAnotherValue; ... } tStateMessage; #pragma pack(pop) //... send via socket tStateMessage msg; send(iSocketFD,(void*)(&msg),sizeof(tStateMessage)); //... receive message on the other side tStateMessage msg_received; recv(iSocketFD,(void*)(&msg_received),sizeof(tStateMessage)); Additionally... Since both endpoints are little endian maschines, endianess is not a problem here. And the pack #pragma solves alignment issues satisfactorily. Thx for your answers, Axel

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  • Pass enum value to method which is called by dynamic object

    - by user329588
    hello. I'm working on program which dynamically(in runtime) loads dlls. For an example: Microsoft.AnalysisServices.dll. In this dll we have this enum: namespace Microsoft.AnalysisServices { [Flags] public enum UpdateOptions { Default = 0, ExpandFull = 1, AlterDependents = 2, } } and we also have this class Cube: namespace Microsoft.AnalysisServices { public sealed class Cube : ... { public Cube(string name); public Cube(string name, string id); .. .. .. } } I dynamically load this dll and create object Cube. Than i call a method Cube.Update(). This method deploy Cube to SQL Analysis server. But if i want to call this method with parameters Cube.Update(UpdateOptions.ExpandFull) i get error, because method doesn't get appropriate parameter. I have already tried this, but doesn't work: dynamic updateOptions = AssemblyLoader.LoadStaticAssembly("Microsoft.AnalysisServices", "Microsoft.AnalysisServices.UpdateOptions");//my class for loading assembly Array s = Enum.GetNames(updateOptions); dynamic myEnumValue = s.GetValue(1);//1 = ExpandFull dynamicCube.Update(myEnumValue);// == Cube.Update(UpdateOptions.ExpandFull) I know that error is in parameter myEnumValue but i don't know how to get dynamically enum type from assembly and pass it to the method. Does anybody know the solution? Thank you very much for answers and help!

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  • App engine datastore - query on Enum fields.

    - by Gopi
    I am using GAE(Java) with JDO for persistence. I have an entity with a Enum field which is marked as @Persistent and gets saved correctly into the datastore (As observed from the Datastore viewer in Development Console). But when I query these entities putting a filter based on the Enum value, it is always returning me all the entities whatever value I specify for the enum field. I know GAE java supports enums being persisted just like basic datatypes. But does it also allow retrieving/querying based on them? Google search could not point me to any such example code. Details: I have printed the Query just before being executed. So in two cases the query looks like - SELECT FROM com.xxx.yyy.User WHERE role == super ORDER BY key desc RANGE 0,50 SELECT FROM com.xxx.yyy.User WHERE role == admin ORDER BY key desc RANGE 0,50 Both above queries return me all the User entities from datastore in spite of datastore viewer showing some Users are of type 'admin' and some are of type 'super'.

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  • C++ enum casting and templates

    - by JP
    I get the following error with VS2008: Conversion to enumeration type requires an explicit cast (static_cast, C-style cast or function-style cast) When casting a down casting a ClassA to ClassA_1 and ClassA_1 is a templated class that received an enum for parameter such as: ClassA { virtual ~ClassA(){}; } template <class Param1> ClassA_1 : public ClassA { public: //constructor ClassA_1(Param1 p1) { _p1 = p1; } Param1 _p1; } So I have a upcasted ClassA a = new ClassA_1<myenum>(); When I need to do this: ClassA_1<myenum> a1 = (ClassA_1<myenum> a); // This fails ... The only way it works is: ClassA_1<int> a1 = (ClassA_1<int> a); but this break my template as it must always deal with int... How to properly cast a enum that is now a int, back into the enum?

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  • Is it a bad practice to include all the enums in one file and use it in multiple classes?

    - by Bugster
    I'm an aspiring game developer, I work on occasional indie games, and for a while I've been doing something which seemed like a bad practice at first, but I really want to get an answer from some experienced programmers here. Let's say I have a file called enumList.h where I declare all the enums I want to use in my game: // enumList.h enum materials_t { WOOD, STONE, ETC }; enum entity_t { PLAYER, MONSTER }; enum map_t { 2D, 3D }; // and so on. // Tile.h #include "enumList.h" #include <vector> class tile { // stuff }; The main idea is that I declare all enums in the game in 1 file, and then import that file when I need to use a certain enum from it, rather than declaring it in the file where I need to use it. I do this because it makes things clean, I can access every enum in 1 place rather than having pages openned solely for accessing one enum. Is this a bad practice and can it affect performance in any way?

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  • Enum type constraints in C#

    - by Taylor L
    What is the reason behind C# not allowing type constraints on Enum's? I'm sure there is a method behind the madness, but I'd like to understand why it's not possible. Below is what I would like to be able to do (in theory). public static T GetEnum<T>(this string description) where T : Enum { ... }

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