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Single Object Property Database

, 30 Oct 2007
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Object Properties Snapshot Management

Introduction

It's a very common practice to use the MVC (Model-View-Controller) pattern in modern applications, especially if the application consists of a few logical parts of the independent modules which communicate among them. Very often in such kinds of applications, we meet a huge number of objects on the view layer of the pattern. It's also very common that a user can operate on objects, modify their properties, move them, delete them or add new objects. As a result, the data layer will be modified.

Recently, I was working on a similar project which necessitated showing the user thousands of objects simultaneously. Every single object can be configured separately, which modification can change the schema representation and logical work flow of the application. In these cases, it is better to try to minimize the amount of memory occupied by the application, but also not limit the user to configuring any objects or their properties on the view.

Background

Here, I try to implement the idea of the "property snapshot" in some lines of the code. The idea is quite simple and the implementation, as well. Let's say I have an object of ObjDef type that represents some logical operation. The user schema consists of thousands of ObjDef objects. So, I create one central database that registers the object and saves its definition of properties. The object type will be considered like a key during the registration. So, even if we have a few ObjDefs, the registration will take it only once. Let's look at an example.

Using the Code

Ok, first of all, we need to prepare our ObjDef class for registering with PropertyMapper. PropertyMapper is the main class for managing property snapshots. For every property that we intend to save with a snapshot, we have to add the MapPropertyAttribute attribute. Let's define the class ObjDef.

public class ObjectDef
{
        int intValue  = 0;
        string strValue = "Val";
        public enum ValuesEnum: int { High, Medium, Normal, Small, Lowest };
        private ValuesEnum valuesEnum = ValuesEnum.Normal;


        [MapPropertyAttribute]
        public ValuesEnum Values
        {
            get
            {
                return valuesEnum;
            }
            set
            {
                valuesEnum  = value;
            }
        }

        [MapPropertyAttribute(StandardValue = 1)]
        public int IntValue
        {
            get { return intValue; }
            set { intValue = value; }
        }


        [MapPropertyAttribute(StandardValue = "Hello")]
        public string StrValue
        {
            get { return strValue; }
            set { strValue = value; }
        }

}

The StandartValue parameter of the attribute defines the rule for property management. The snapshot of this property will be saved only if its value is different from the StandartValue. If we don't define the StandartValue, the snapshot for that property will always be saved. The property can also be registered "manually," without use of the MapPropertyAttribute attribute. In that case, the RegisterProperty(objectType,propertyName) method has to be called. Obviously, it can be very useful in cases where you work on the objects and haven't the source code of them. Ok, now let's look at another couple lines of code.

PropertyMaper pm = new PropertyMaper();     
pm.RegisterObject(typeof(ObjDef));
 
//   or

pm.RegisterProperty(typeof(ObjDef),"Values");
pm.RegisterProperty(typeof(ObjDef),"IntValue");
pm.RegisterProperty(typeof(ObjDef),"StrValue");


//create the object
ObjDef single = new ObjDef();

for (int i = 0; i < 100000; i++)
{
      single.IntValue = 100 + i;
      single.StrValue = i.ToString();
      single.Values = (Objects.ObjectDef.ValuesEnum)(i % 5);
      pm.SaveObjectProperties(single, "UNIQUE_" + i);                
}

The pm.SaveObjectProperties(..) function gets following parameters:

  • The object itself, which will be scanned for all properties marked with the MapPropertyAttribute and saved
  • The UNIQUE key identifier that we need to preserve in order to get the saved snapshot values in the moment we need

For example, to get the first snapshot in our case, we need to write:

pm.FillObjectProperties(single, "UNIQUE_" +0);

The single object will be filled with the values of properties saved in the snapshot before, with key value UNIQUE_0.

Points of Interest

As I mentioned before, the idea is quite simple and the implementation, too. This implementation operates only on the properties of the objects, which means that properties must have the read/write access parameters. If a property's return value is the reference type, it must be cloned. In consequence, it must implement the IClonable interface. This model uses reflection to examine the object and, afterwards, access its properties. This obviously creates some application speed performance overhead. It's almost two times slower with respect to the version where we create 100,000 objects and directly access their properties.

Even with these difficulties, in our particular case, we achieve our goal. This is because, even with less speed, we get more than 30% less memory usage and don't limit to the user to accessing any property of any object. I hope my solution will help someone in his work or, if not, will help to design and implement more potential ways of managing object properties in his application.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Tigran Martirosyan

United States United States
No Biography provided

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Comments and Discussions

 
Questionwhy not just use Serialization? Pinmemberdimzon30-Oct-07 7:31 
AnswerRe: why not just use Serialization? [modified] PinmemberNardi30-Oct-07 8:01 

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