Hi,
I have some enum (enumeration ) defined in some namespace, not inside
class. How to use the enum constant's in some other namespace without
using the whole namespace.
To say in little detail, the enum is declared as,
namespace test{
enum MyEnum{
VALUE1,VALUE2
};
}
now in another namespace,
using test::MyEnum; //It gets myenum.
MyEnum e = VALUE1; //It doesnt get the value.
One solution is to have using test::VALUE1;
but as such enum const's are huge in number it is not possible to use
all of them seperately.
Other way is to have using namespace test; But the namespace has many
other things and I want to avoid such statement if possible.
It looks the enum constants are 'free' inside the namespace, not
guarded by the MyEnum.
Anyway to deal with it? Is it possible to enclose them inside a dummy
class and use them ?
Sep 21 '06
13 18150
Jens Theisen wrote:
Comeau and gcc disagree, so I guess it's nonstandard. What compiler do
you use?
I think so too.
>
I don't know of a way to practically forward declare an enum in a
standard way or a feasible workaround. If someone does, I'd like to
hear.
I don't think there is one. I don't know why, but think there may be
good reason. Maybe some std guru can comment :-). The fact that comeau
does not compile it, makes me wonder. I know VCC does compile it, but I
work on more than one compiler - 4 to be precise (5 comeau included).
An alternative is to wrap it in a namespace:
The problem with wrapping in a namespace, is that each value that forms
part of the enum must be explicitly qualified (I think).
therefore...
using MyEnum::enum_t;
int x = static_cast<int >(eSome); //error, no type eSome
// in scope, required to qualify with MyEnum...
Regards,
Werner
"werasm" <w_*****@telkom sa.netwrites:
The problem with wrapping in a namespace, is that each value that forms
part of the enum must be explicitly qualified (I think).
therefore...
using MyEnum::enum_t;
int x = static_cast<int >(eSome); //error, no type eSome
// in scope, required to qualify with MyEnum...
Not if you use a using directive:
using namespace MyEnum;
^^
Regards,
Jens
Jens Theisen wrote:
"werasm" <w_*****@telkom sa.netwrites:
Not if you use a using directive:
using namespace MyEnum;
Yes, true. Unfortunately this is not a good idea in an .h file (for
qualification in class definitions). In general, it is not common to
use enum values in class definitions, though. If the need was required,
using an anonymous enum with a class is quite handy.
struct someS{
typedef x::y::z enum_t enum_t;
//now values qualified here by enum_t::value;
};
I have also found that the class name can form part of the actual enum
name (nice feature for categorisation) . This could be true for
namespaces too, though.
struct State
{
enum
{
Standby, Maintenance, Operational, Shutdown
};
};
Now qualify like:
State::Standby etc... The qualifier name conveys information about the
category of the enumerated type. A feature we often use. The biggest
reason for doing this though, is the fact that forward declaration of
enums don't work. If that was not the case, I would probably consider
using namespaces to scope my enums like you propose.
Regards,
Werner
Jens Theisen wrote:
"mlimber" <ml*****@gmail. comwrites:
This is entirely unnecessary since you can forward-declare enums
without the struct:
Comeau and gcc disagree, so I guess it's nonstandard. What compiler do
you use?
How about that? Comeau and gcc do issue a warning, but VC++ 6, 7, 7.1,
8, and (most surprisingly) EDG don't.
I don't know of a way to practically forward declare an enum in a
standard way or a feasible workaround. If someone does, I'd like to
hear.
How about the technique presented here: http://www.ddj.com/dept/cpp/184403894
Cheers! --M This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
by: Marshall Mills |
last post by:
As I understand it, loaded statement, a using declaration should be all I
need to see an enum from within a namespace. The below code works fine with
class, struct, and union. What gives? As the code says, if I employ the
using directive, I'm ok.
/* built with Visual C++ 6, SP 5 */
namespace Traffic
{
enum Light { red, yellow, green };
}
|
by: Bilgehan.Balban |
last post by:
Hi,
I have two different enum definitions with members of same name. The
compiler complains about duplicate definitions. Is this expected
behaviour?
Can't I have same-named fields in different enum definitions? I think
it should have been perfectly valid to do that. Its a stupid limitation
to have to define disjoint enum symbol definitions. This is like having
to have disjoint member names in structures.
|
by: msnews.microsoft.com |
last post by:
How do I get Intellisense to open a dropdown list box for a method's
parameters when the parameter is an ENUM?
public class MyClass
{
public enum IDkind
{
PersonID,
EntityID,
PlaceID
|
by: Joe |
last post by:
I have a .cs file which is linked to several other projects. All my classes
in this file are defined as internal. I would like to have an enum defined
as well in the namespace but I get an error from one project that the
accessibility of the enum is less (public) than that of a method which
returns that's type.
What is the best way to define this enum without getting duplicate define
warnings or this error of less accessibility?
...
|
by: Andrea Williams |
last post by:
I'm working with C# and I'm setting up some ENUM's I have a data and
Business layer. I'm declaring a common enum for the Data Layer. The UI
layer references the Bus layer and the bus layer references the Data layer,
but I would like to have the enum exposed to all three. Is there a way to
trickle down that enum (Like class inheritance exposes classes) so that it
can be accessed from the Business layer and UI layers? My UI layer doesn't...
| |
by: toton |
last post by:
I have an enum in a namespace like,
namespace client{
namespace ui{
enum InkEnum{
ID_INK_COLOR,
ID_INK_WIDTH,
};
class InkEventHandler{
...
};
|
by: Steven Nagy |
last post by:
So I was needing some extra power from my enums and implemented the
typesafe enum pattern.
And it got me to thinking... why should I EVER use standard enums?
There's now a nice little code snippet that I wrote today that gives me
an instant implementation of the pattern. I could easily just always
use such an implementation instead of a standard enum, so I wanted to
know what you experts all thought.
Is there a case for standard enums?
|
by: Cmtk Software |
last post by:
I'm trying to define an enum which will be used from unmanaged c++, C++/CLI
managed c++ and from C#.
I defined the following enum in a VS dll project set to be compiled with the
/clr switch:
public enum Days
{
Sunday
};
|
by: hufaunder |
last post by:
Imagine you have a charting library that can draw lines, bars,
floating bars, bands, etc.
Lines and bars need only one input. Floating bars and bands need two
inputs. There are two approaches:
1) One enum with all 4 types (bars, band, etc). One chart class that
accepts up to 2 arrays of values. If the user choses a band but there
is only one input array throw an exception. If the user passes two
input arrays with different lengths throw...
|
by: marktang |
last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look !
Part I. Meaning of...
|
by: Oralloy |
last post by:
Hello folks,
I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>".
The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed.
This is as boiled down as I can make it.
Here is my compilation command:
g++-12 -std=c++20 -Wnarrowing bit_field.cpp
Here is the code in...
| |
by: jinu1996 |
last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth.
The Art of Business Website Design
Your website is...
|
by: agi2029 |
last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own....
Now, this would greatly impact the work of software developers. The idea...
|
by: isladogs |
last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM).
In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules.
He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms.
Adolph will...
|
by: conductexam |
last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one.
At the time of converting from word file to html my equations which are in the word document file was convert into image.
Globals.ThisAddIn.Application.ActiveDocument.Select();...
|
by: adsilva |
last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
|
by: muto222 |
last post by:
How can i add a mobile payment intergratation into php mysql website.
| |
by: bsmnconsultancy |
last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...
| |