Question

Here’s my problem:

• I have two classes: ClassObj and ClassProperty;
• One of the properties of ClassObj (let’s call it lstProperty) is a List of ClassProperty (representing the property that current instance of the object have);
• At runtime I have stored somewhere an Array of all possible ClassProperty, we will call this Array arrPossibleProperty.

My issue is to find a REALLY fast way of checking if an instance of ClassObj match a particular set of ClassProperty (if he have in his lstProperty all the ClassProperty of a given set).

I was thinking about creating an array of Bit representing the sequence of ClassProperty that the ClassObj posesses. Using as reference the Array arrPossibleProperty, and the index of his Property.

So if for example we have 10 property and a InstanceA of ClassObj have the 1st the 4th and the 9th I would generate this array of bit:
1001000010

My question is, how can I check for example (Fastest and Most performing solution) that the array of bit have (for example) the 3rd and the 4th Property?

Of course if you need there’s a more performing way of doing this let me know.

Answer 1

You’ll want to use bitwise-operations, such as &, |, ^ or ~ (depending on your needs)

Taking your example of 1001000010, to find out if the 3rd bit is set, you’d want to do this: 1001000010 & 0000000100 != 0000000000, or rather

bool isSet = myProperty & (1 << (option - 1)) != 0; // to find out if `myProperty` has the property `option` set.
myProperty |= 1 << (option -  1); // to set property `option`

For more information about bitwise operations: http://en.wikipedia.org/wiki/Bitwise_operation

Alternatively and a lot more easy to implement, would be using enums.

[Flags]
enum ClassProperty
{
    None = 0x00,
    First = 0x01,
    Second = 0x02,
    Third = 0x04,
    Fourth = 0x08
    // add more if needed
}

Then, you’d use the enum like this

myProperty = ClassProperty.First | ClassProperty.Second; // sets both First and Second
bool thirdIsSet = myProperty.HasFlag(ClassProperty.Third);