Get all containing flags

Question

I have a variable containing some flags and wounder how I'm able to check which flags that are set.

My flags.

[Flags]
    public enum Button{ 
        //Can't have more than 30 flags
        //If an enum is added or deleted need to change for loop in method AddButton

        // Exit flags
        Exit = 1 << 0, 
        Cancel = 1 << 1, 
        Abort = 1 << 2,
        Close = 1 << 3,

        //Proced flags
        Accept = 1 << 4, 
        Ok = 1 << 5,
        Submit = 1 << 6,

        //Question flags
        No = 1 << 7,
        Yes = 1 << 8,

        //Save and load
        Save = 1 << 9,
        SaveAll = 1 << 10,
        SaveNew = 1 << 11,
        Open = 1 << 12,
        Load = 1 << 12
    }

And here are where i check my flags

    for (int i = 1; i <= 12; ++i) {
        if((buttons & 1 << i) == 1 << i){

        }
    }

Apparently I can't use this way to check flags.

To be clear I want to know what flags that are set in buttons.

Update: I can't use the Enum.hasFlag() because I making a game in Unity and it uses Mono. Apparently Mono hasn't support for hasFlag yet.

Why can't you do that? Looks like it would work to me, with the exception that you are off by one because you start with `i=1` and shift on top of that, so you can't test for Exit. Granted it isn't very language like in C# but it should do what you want. BTW [Enum.HasFlag](https://msdn.microsoft.com/en-us/library/system.enum.hasflag%28v=vs.110%29.aspx) is the built in way to do that. — Frank J, Jun 04 '15 at 17:54
I'll get this error " Operator `&' cannot be applied to operands of type `Window.Button' and `int' ". I would love to use Enum.HasFlag but I use Mono and it seams Mono hasn't implemented it yet. — Olof, Jun 04 '15 at 18:00
Pretty fishy code. it never makes sense to let a button implement multiple operations. It will Save or Open, not both. Remove [Flags]. — Hans Passant, Jun 04 '15 at 18:11
As @Sam S wrote just cast it. But again this is not very language like — Frank J, Jun 04 '15 at 18:13

Cortright · Answer 1 · 2015-06-04T19:18:12.780

I pulled this from this article, which is pretty helpful. It shows how to use an enum with bit shifting and bitwise information.

http://www.codeducky.org/ins-outs-c-enums/

// this attribute isn't strictly necessary, but it provides
// useful metadata and greatly improves the ToString() representation
[Flags]
enum BookFlags
{
    // most flags enums provide a named None or Default
    // zero value to represent the empty set
    Default = 0,
    HardCover = 1,
    InStock = HardCover << 1, // 2
    HasEBook = InStock << 1, // 4
    OnSale = HasEBook << 1, // 8
}

// we can create and test flag sets with bitwise operations
BookFlags flags = BookFlags.HardCover | BookFlags.InStock;
var text = flags.ToString(); // HardCover, InStock
var isInStock = (flags & BookFlags.InStock) == BookFlags.InStock; // true
// testing for a particular flag is also simplified by the HasFlag extension
var isInStock2 = flags.HasFlag(BookFlags.InStock); // true

Edit: You probably want something like this, if you can't use HasFlag.

// i redefined your enum a bit
public enum Buttons
{
    // Default
    Default = 0,

    // Exit flags
    Exit = 1,
    Cancel = Exit << 1,
    Abort = Cancel << 1,
    Close = Abort << 1,

    //Proced flags
    Accept = Close << 1,
    Ok = Accept << 1,
    Submit = Ok << 1,

    //Question flags
    No = Submit << 1,
    Yes = No << 1,

    //Save and load
    Save = Yes << 1,
    SaveAll = Save << 1,
    SaveNew = SaveAll << 1,
    Open = SaveNew << 1,
    Load = Open << 1
}

And then you can...

        // here's checking a selection of buttons against the complete enum universe of values
        var lastButton = Convert.ToInt32(Enum.GetValues(typeof(Buttons)).Cast<Buttons>().Max());
        int enumCheck;

        Buttons flags = Buttons.Ok | Buttons.SaveNew | Buttons.Load | Buttons.No | Buttons.Submit | Buttons.Exit;

        for (int i = 0; Math.Pow(2, i) <= lastButton; i++)
        {
            enumCheck = (int)Math.Pow(2, i);

            if ((flags & (Buttons)enumCheck) == (Buttons)enumCheck)
            {
                Debug.WriteLine(Enum.GetName(typeof(Buttons), enumCheck));
            }
        }

Produces output (notice the order):

Exit
Ok
Submit
No
SaveNew
Load

score 1 · Accepted Answer · answered Jun 04 '15 at 18:04

1

Just cast buttons to int. And you might want to make sure your loop starts with 0, or you'll miss one check.

for (int i = 0; i <= 12; ++i)
{
    if (((int)buttons & 1 << i) == 1 << i)
    {

    }
}

answered Jun 04 '15 at 18:04

sstan

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Get all containing flags

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