how do i switch on an enum which have the flags attribute set (or more precisely is used for bit operations) ?

I want to be able to hit all cases in a switch that matches the values declared.

The problem is that if i have the following enum

    [Flags()]public enum CheckType
	{
		Form = 1,	
		QueryString = 2,
		TempData = 4,
	}

and I want to use a switch like this  

    switch(theCheckType)
    {
       case CheckType.Form:
           DoSomething(/*Some type of collection is passed */);
           break;
    
       case CheckType.QueryString:
           DoSomethingElse(/*Some other type of collection is passed */);
           break;
    
       case CheckType.TempData
           DoWhatever(/*Some different type of collection is passed */);
           break;
    }

If &quot;theCheckType&quot; is set to both CheckType.Form | CheckType.TempData I want it to hit both case&#39;s. Obviously it wont hit both in my example because of the break, but other than that it also fails because CheckType.Form is not equal to CheckType.Form | CheckType.TempData

The only solution then as I can see it is to make a case for every possible combination of the enum values ?

Something like

        case CheckType.Form | CheckType.TempData:
            DoSomething(/*Some type of collection is passed */);
            DoWhatever(/*Some different type of collection is passed */);
            break;
        
        case CheckType.Form | CheckType.TempData | CheckType.QueryString:
            DoSomething(/*Some type of collection is passed */);
            DoSomethingElse(/*Some other type of collection is passed */);
            break;
    
    ... and so on...

But that really isnt very desired (as it will quickly grow very big)

Right now i have 3 If conditions right after eachother instead

Something like 

    if ((_CheckType &amp; CheckType.Form) != 0)
    {
        DoSomething(/*Some type of collection is passed */);
    }
    
    if ((_CheckType &amp; CheckType.TempData) != 0)
    {
        DoWhatever(/*Some type of collection is passed */);
    }
    
    ....

But that also means that if i have an enum with 20 values it have to go through 20 If conditions every single time instead of &quot;jumping&quot; to only the needed &quot;case&quot;/&#39;s as when using a switch.

Is there some magic solution to solve this problem?

I have thought of the possibility to loop through the declared values and then use the switch, then it would only hit the switch for each value declared, but I don&#39;t know how it will work and if it performance vice is a good idea (compared to a lot of if&#39;s) ?

Is there an easy way to loop through all the enum values declared ?

I can only come up with using ToString() and splitting by &quot;,&quot; and then loop through the array and parse every single string.


_________
UPDATE:

I see that i haven&#39;t done a good enough job explaining.
My example is to simple (tried to simplify my scenario).

I use it for a ActionMethodSelectorAttribute in Asp.net MVC to determine if a method should be available when resolving the url/route.

I do it by declaring something like this on the method

    [ActionSelectorKeyCondition(CheckType.Form | CheckType.TempData, &quot;SomeKey&quot;)]
    public ActionResult Index()
    {
        return View();
    } 

That would mean that it should check if the Form or TempData have a key as specified for the method to be available. 

The methods it will be calling (doSomething(), doSomethingElse() and doWhatever() in my previous example) will actually have bool as return value and will be called with a parameter (different collections that doesn&#39;t share a interface that can be used - see my example code in the link below etc).

To hopefully give a better idea of what i am doing i have pasted a simple example of what i am actually doing on pastebin - it can be found here [http://pastebin.com/m478cc2b8][1]


  [1]: http://pastebin.com/m478cc2b8

Switch on Enum (with Flags attribute) without declaring every possible combination?

I have a problem with flag bits.
I have an `int` variable to hold flags. First I set some flags to that variable. Later I need check how many flags were set in that variable. But I don&#39;t know to do it.

Checking flag bits java

For testing purposes only, I am allowing my app APK to be downloaded and installed via a URL. Once downloaded on the phone, it can be launched with the Android app installer which gives the user an option to install it to their device and then run it.

Consider if we downloaded and ran the app in the way described above. The main/launcher activity in my app is a login page (`Activity A`). Once the user is authenticated, they are taken to the main area of the application, e.g. `Activity B`. So now the current activity stack of this task is `A &gt; B`.

I then press the home button on the phone and am taken to the Android home screen. I re-launch my app via the icon in the menu, and I am taken to `Activity A`, instead of `Activity B`. Either the activity stack is now `A &gt; B &gt; A`, or there are now two separate tasks with activity stacks `A &gt; B`, and `A` respectively. What I want is to be taken back to `Activity B` when I relaunch the app. Pressing back whilst in this state will take me back to `Activity B`.

This undesired behaviour only happens if I first open the app via the installer, and not if I open the app via the home screen/menu.

I looked into how the activities are being started by each mechanism. When we use the app installer, we see the following logs:

    INFO/ActivityManager(XXXX): Starting activity: Intent { dat=file:///mnt/sdcard/download/[my app].apk cmp=com.android.packageinstaller/.InstallAppProgress (has extras) }
    INFO/ActivityManager(XXXX): Starting activity: Intent { act=android.intent.action.MAIN flg=0x10000000 cmp=[my package]/[Activity A] }

via launcher / home screen:

    INFO/ActivityManager(XXXX): Starting activity: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=[my package]/[Activity A] }


When started with the installer we see it is using the flag `0x10000000`, but when started with the launcher we see it is using `0x10200000`. It is also using an intent category.

From the [docs][1] we see the flags are:

    public static final int FLAG_ACTIVITY_NEW_TASK
    Constant Value: 268435456 (0x10000000)

    public static final int FLAG_ACTIVITY_RESET_TASK_IF_NEEDED
    Constant Value: 2097152 (0x00200000)

The flag `FLAG_ACTIVITY_RESET_TASK_IF_NEEDED` (which is being used when the app is launched from the launcher) seems to usually prevent a new task from being created if one already exists, and will restore the last used activity. This is the desired behaviour. Why is it not working in this situation? Is there anything I can do to make sure my application will always return me to the last Activity regardless of whether it was started through the app installer/launcher?

If I use `singleTask` it will always take me back to the main activity (`Activity A`) whenever I run the app (which is also not desirable).

Here is a question I found where someone is experiencing a similar problem (which has no accepted answer): https://stackoverflow.com/questions/5318885/app-loses-its-ability-to-remember-its-stack-when-launched-from-another-applicatio

EDIT: Checking for the flag `FLAG_ACTIVITY_BROUGHT_TO_FRONT` in `onCreate()` of our launcher activity (and then finishing if it is set) seems to fix the main symptom, but clearly the underlying issue is still there. Is there a more complete fix?

EDIT2: The same result occurs when you download/run the app from the Android Market, so some of the above details may not be relevant.

  [1]: http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_NEW_TASK

Activity stack ordering problem when launching application from Android app installer and from Home screen

I have some heavily instrumented code that makes use of the `log` package. Now it&#39;s come time to turn off the logging, and I can&#39;t determine how to turn off the standard logger.

Have I missed something? Should I be checking a flag before making log calls, or commenting them out in production?

How to disable a log.Logger

Let&#39;s say I have this enum:

    [Flags]
    enum Letters
    {
         A = 1,
         B = 2,
         C = 4,
         AB = A | B,
         All = A | B | C,
    }

To check if for example `AB` is set I can do this:

    if((letter &amp; Letters.AB) == Letters.AB)

Is there a simpler way to check if any of the flags of a combined flag constant are set than the following?

    if((letter &amp; Letters.A) == Letters.A || (letter &amp; Letters.B) == Letters.B)

Could one for example swap the `&amp;` with something?



How to check if any flags of a flag combination are set?

For the life of me, I can&#39;t remember how to set, delete, toggle or test a bit in a bitfield. Either I&#39;m unsure or I mix them up because I rarely need these. So a &quot;bit-cheat-sheet&quot; would be nice to have.

For example: 

    flags = flags | FlagsEnum.Bit4;  // Set bit 4.

or

    if ((flags &amp; FlagsEnum.Bit4)) == FlagsEnum.Bit4) // Is there a less verbose way?

Can you give examples of all the other common operations, preferably in C# syntax using a [Flags] enum?


Most common C# bitwise operations on enums

I&#39;m trying to write a script that will check two error flags, and in case one flag (or both) are changed it&#39;ll echo-- error happened. My script:

    my_error_flag=0
    my_error_flag_o=0
    do something.....
    if [[ &quot;$my_error_flag&quot;==&quot;1&quot; || &quot;$my_error_flag_o&quot;==&quot;2&quot; ] || [ &quot;$my_error_flag&quot;=&quot;1&quot; &amp;&amp;     &quot;$my_error_flag_o&quot;=&quot;2&quot; ]]; then
        echo &quot;$my_error_flag&quot;
    else
        echo &quot;no flag&quot;
    fi

Basically, it should be, something along:
    
    if ((a=1 or b=2) or (a=1 and b=2))
      then
         display error
    else
         no error
    fi

The error I get is:

     line 26: conditional binary operator expected
     line 26: syntax error near `]&#39;
     line 26: `if [[ &quot;$my_error_flag&quot;==&quot;1&quot; || &quot;$my_error_flag_o&quot;==&quot;2&quot; ] || [ &quot;$my_error_flag&quot;=&quot;1&quot; &amp;&amp; &quot;$my_error_flag_o&quot;=&quot;2&quot; ]]; then&#39;

Are my brackets messed up?

Bash if statement with multiple conditions throws an error

There is a variable that holds some flags and I want to remove one of them. But I don&#39;t know how to remove it.

Here is how I set the flag.

    my.emask |= ENABLE_SHOOT;



How can I remove a flag in C?

Why are people always using enum values like `0, 1, 2, 4, 8` and not `0, 1, 2, 3, 4`?

Has this something to do with bit operations, etc.?

I would really appreciate a small sample snippet on how this is used correctly :)

    [Flags]
    public enum Permissions
    {
        None   = 0,
        Read   = 1,
        Write  = 2,
        Delete = 4
    }


Why do enum permissions often have 0, 1, 2, 4 values?

I have a flag enum below.

    [Flags]
    public enum FlagTest
    {
        None = 0x0,
        Flag1 = 0x1,
        Flag2 = 0x2,
        Flag3 = 0x4
    }

I cannot make the if statement evaluate to true.


    FlagTest testItem = FlagTest.Flag1 | FlagTest.Flag2;
    
    if (testItem == FlagTest.Flag1)
    {
        // Do something,
        // however This is never true.
    }

How can I make this true?

How to Compare Flags in C#?

I have seen lots of ways of running Perl code or scripts, with different flags. However, when I try to google for what each flag means, I mainly get results to generic Perl sites and no specific information regarding the flags or their use is found there.

Below are the flags that I encounter most often, and I don&#39;t have a clue what they mean:

 - perl **-pe**
 - perl **-pi**
 - perl **-p**
 - perl **-w**
 - perl **-d**
 - perl **-i**
 - perl **-t**

I will be very grateful if you tell me what each of those mean and some use cases for them, or at least tell me a way of finding out their meaning.


Perl flags -pe, -pi, -p, -w, -d, -i, -t?

Found an interesting JVM Flag :

    java -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal -version

It prints hundreds of various options, I never heard about before. 
It also prints default values, that helps diagnose JVM behaviors better.
Another interesting flag is: 

    -XX:+UnlockExperimentalVMOptions

Does anyone knows of any documentation which explains each one of them ?

Print All JVM Flags

I tried to scrub the GCC man page for this, but still don&#39;t get it, really.

What&#39;s the difference between `-march` and `-mtune` ?

When does one use just `-march`, vs. both? Is it ever possible to just `-mtune`?

GCC: how is march different from mtune?

What I want to do is something like this: I have enums with combined flagged values.

    public static class EnumExtension
    {
    	public static bool IsSet&lt;T&gt;( this T input, T matchTo ) 
            where T:enum //the constraint I want that doesn&#39;t exist in C#3
    	{    
    		return (input &amp; matchTo) != 0;
    	}
    }

So then I could do:

    MyEnum tester = MyEnum.FlagA | MyEnum.FlagB
    
    if( tester.IsSet( MyEnum.FlagA ) )
        //act on flag a

Unfortunately, C#&#39;s generic where constraints have no enum restriction, only class and struct. C# doesn&#39;t see enums as structs (even though they are value types) so I can&#39;t add extension types like this.

Does anyone know a workaround?

Anyone know a good workaround for the lack of an enum generic constraint?

I&#39;m trying to update my C++ compiler to C++11.
I have searched a bit and I have come to the conclusion that I have to use the flag `-std=c++0x` or `-std=gnu++0x`, but I don&#39;t know many things about flags. Can anyone help me? (I&#39;m using Ubuntu 12.04.)

Here is the error that I get from the compiler when I attempt to use a library which is included in C++11 (i.e. array):

    #include &lt;array&gt;
    #include &lt;iostream&gt;
    
    int main()
    {
        std::array&lt;int, 3&gt; arr = {2, 3, 5};
        ...
    }
    

&gt; This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options.

Compiling C++11 with g++

Currently I&#39;m starting a new `Activity` and calling `finish` on a current one.

Is there any flag that can be passed to `Intent` that enables finishing current `Activity` without a need to call `finish` manually from code?



Start new Activity and finish current one in Android?

From time to time I see an enum like the following:

    [Flags]
    public enum Options 
    {
        None    = 0,
        Option1 = 1,
        Option2 = 2,
        Option3 = 4,
        Option4 = 8
    }

I don&#39;t understand what exactly the `[Flags]` attribute does.

Anyone have a good explanation or example they could post?

What does the [Flags] Enum Attribute mean in C#?

I used:

    getWindow().addFlags(android.view.WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

How do I resume to Default state (no-keep-on)?

Disable keep screen on

I need to emulate enum type in Javascript and approach seems pretty straight forward:

    var MyEnum = {Left = 1; Right = 2; Top = 4; Bottom = 8}

Now, in C# I could combine those values like this:

    MyEnum left_right = MyEnum.Left | MyEnum.Right

and then I can test if enum has certain value:

    if (left_right &amp; MyEnum.Left == MyEnum.Left) {...}

Can I do something like that in Javascript?

Enum flags in JavaScript

Do you know any Java cookie implementation which allows to set a custom flag for cookie, like `SameSite=strict`? It seems that [`javax.servlet.http.Cookie`][1] has a strictly limited set of flags which can be added.


  [1]: https://docs.oracle.com/javaee/7/api/javax/servlet/http/Cookie.html

SameSite cookie in Java application

I am using Enum flags in my application. The Enum can have around 50+ values, so values go up to 2^50. I was just wondering, can I use `Math.Pow(2, variable)` to calculate these?

When I try to do that I get a *constant value* compile-time error. Is there another way, other than calculating these powers of 2 manually and putting it in?

Here&#39;s what I am doing:

    [Flags]
    internal enum RiskStates : long
        {
            None = 0,
            AL = Convert.ToInt64(Math.Pow(2,0)),
            AK = 2,
            AZ = 4,
            AR = 8,
            CA = 16,
            CO = 32,
            CT = 64,
            DC = 128,
            DE = 256,
            FL = 512,
            GA = 1024,
            HI = 2048,
            ID = 4096,
            IL = 8192,
            IN = 16384,
            IA = 32768,
            KS = 65536,
            KY = 131072,
            LA = 262144,
            ME = 524288,
            MD = 1048576,
            MA = 2097152,
            MI = 4194304
    }


Enum flags over 2^32

In the middle of a script, I want to check if a given flag was passed on the command line. The following does what I want but seems ugly:

    if echo $* | grep -e &quot;--flag&quot; -q
    then
      echo &quot;&gt;&gt;&gt;&gt; Running with flag&quot;
    else
      echo &quot;&gt;&gt;&gt;&gt; Running without flag&quot;
    fi

*Is there a better way?*

Note: I explicitly *don&#39;t* want to list all the flags in a switch/getopt. (In this case any such things would become half or more of the full script. Also the bodies of the if just set a set of vars) 

Correct way to check for a command line flag in bash

I find out that we can use cool flags that scroll both toolbar and even content by using `layout_scrollFlags`. In my case, I have a layout like this:

    &lt;android.support.design.widget.CoordinatorLayout xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
        xmlns:app=&quot;http://schemas.android.com/apk/res-auto&quot;
        android:layout_width=&quot;match_parent&quot;
        android:layout_height=&quot;match_parent&quot;&gt;
    
        &lt;android.support.design.widget.AppBarLayout
            android:layout_width=&quot;match_parent&quot;
            android:layout_height=&quot;wrap_content&quot;
            android:theme=&quot;@style/ThemeOverlay.AppCompat.Dark.ActionBar&quot;&gt;
    
            &lt;android.support.v7.widget.Toolbar
                android:id=&quot;@+id/toolbar&quot;
                android:layout_width=&quot;match_parent&quot;
                android:layout_height=&quot;?attr/actionBarSize&quot;
                android:background=&quot;?attr/colorPrimary&quot;
                app:layout_scrollFlags=&quot;snap&quot;
                app:popupTheme=&quot;@style/ThemeOverlay.AppCompat.Light&quot; /&gt;
    
            &lt;android.support.design.widget.TabLayout
                android:id=&quot;@+id/tabs&quot;
                android:layout_width=&quot;match_parent&quot;
                android:layout_height=&quot;wrap_content&quot;
                app:tabMode=&quot;fixed&quot;
                app:tabGravity=&quot;fill&quot; /&gt;
        &lt;/android.support.design.widget.AppBarLayout&gt;
    
        &lt;android.support.v4.view.ViewPager
            android:id=&quot;@+id/viewpager&quot;
            android:layout_width=&quot;match_parent&quot;
            android:layout_height=&quot;match_parent&quot;
            app:layout_behavior=&quot;@string/appbar_scrolling_view_behavior&quot; /&gt;
    &lt;/android.support.design.widget.CoordinatorLayout&gt;

one of my tabs is a `fragment` and its layout has a `Recycle View` with a `edittext` below the RecycleView. firstly I wanna know what this flag means  

google says:

 - **SCROLL_FLAG_ENTER_ALWAYS** 	
When entering (scrolling on screen) the view will scroll on any downwards scroll event, regardless of whether the scrolling view is also scrolling. 
 - **SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED** 	
An additional flag for &#39;enterAlways&#39; which modifies the returning view to only initially scroll back to it&#39;s collapsed height. 
 - **SCROLL_FLAG_EXIT_UNTIL_COLLAPSED** 	
When exiting (scrolling off screen) the view will be scrolled until it is &#39;collapsed&#39;. 
 - **SCROLL_FLAG_SCROLL** 	
The view will be scroll in direct relation to scroll events. 
 - **SCROLL_FLAG_SNAP** 	
Upon a scroll ending, if the view is only partially visible then it will be snapped and scrolled to it&#39;s closest edge. 

I changed this flag randomly and in some cases my edit text went away till I scrolled the toolbar up and then edit appeared. I read google documents
but I could not get it well. I want to understand it in simple terms.


All Flags Solutions on Gang of Coders

Total of 23 Flags Solutions