Skip to main content

Flyweight Pattern

Flyweight Pattern 


Gamma Categorization: Structural Design Pattern
Summary:Use sharing to support large numbers of fine-grained objects efficiently.

Sample Code

Problem: We want to store in memory only one object per unique filter definition.

Code

public class Filter
{
    public Guid ID { get; set; }
    public List<string> FilterProperties { get; set; } = new List<string>();

    public bool Equals(Filter filter)
    {
        if(this.FilterProperties.Count != filter.FilterProperties.Count)
            return false;

        this.FilterProperties.Sort();
        filter.FilterProperties.Sort();

        if (!this.FilterProperties.SequenceEqual(filter.FilterProperties))
            return false;

        return true;
    }
}

public class PhotoEditor
{
    private List<Filter> filterCache = new List<Filter>();
    private Dictionary<string,Guid> filters = new Dictionary<string, Guid>();

    public void ApplyFilter(string filterName)
    {
        if(!filters.ContainsKey(filterName))
            return;

        var filterGuid = filters[filterName];
        var filter = filterCache.FirstOrDefault(f => f.ID == filterGuid);

        System.Console.WriteLine($"\nFilter Name: {filterName}");
        System.Console.WriteLine($"Internal Filter ID: {filterGuid}");

        filter.FilterProperties.ForEach(p => System.Console.WriteLine($"\tApplying {p}"));
    }

    public void AddFilter(string filterName, List<string> filterProperties)
    {
        var newFilter = new Filter { ID = Guid.NewGuid(), FilterProperties = filterProperties };

        Guid existingFilterGuid = Guid.Empty;
        foreach (var filter in filterCache)
        {
            if(filter.Equals(newFilter))
            {
                existingFilterGuid = filter.ID;
                break;
            }
        }

        if(existingFilterGuid != Guid.Empty)
            filters.Add(filterName, existingFilterGuid);
        else
        {
            filterCache.Add(newFilter);
            filters.Add(filterName, newFilter.ID);
        }
    }
}

Usage

photoEditor.AddFilter("Preset1", new List<string> { "Contrast" });
photoEditor.AddFilter("Preset2", new List<string> { "Contrast", "Sharpen", "Saturation", "White balance"});
photoEditor.AddFilter("Preset3", new List<string> { "Contrast", "Sharpen", "Saturation", "White balance"});
photoEditor.AddFilter("Preset4", new List<string> { "Saturation" });
photoEditor.AddFilter("Preset5", new List<string> { "Contrast" });

photoEditor.ApplyFilter("Preset1");
photoEditor.ApplyFilter("Preset2");
photoEditor.ApplyFilter("Preset3");
photoEditor.ApplyFilter("Preset4");
photoEditor.ApplyFilter("Preset5");

Output

Filter Name: Preset1
Internal Filter ID: 8d056cb7-9f78-498f-a692-57dfa0674d16
        Applying Contrast

 Filter Name: Preset2
Internal Filter ID: eb0b6b2d-b4ed-43d1-b46b-b1a8ad06cd53
        Applying Contrast
        Applying Saturation
        Applying Sharpen
        Applying White balance

 Filter Name: Preset3
Internal Filter ID: eb0b6b2d-b4ed-43d1-b46b-b1a8ad06cd53
        Applying Contrast
        Applying Saturation
        Applying Sharpen
        Applying White balance

 Filter Name: Preset4
Internal Filter ID: 11ed980b-902a-4e0d-8d9b-05e6908ea2d3
        Applying Saturation

 Filter Name: Preset5
Internal Filter ID: 8d056cb7-9f78-498f-a692-57dfa0674d16
        Applying Contrast

Comments

Post a Comment

Popular posts from this blog

Software Development

Software Development Agile Agile is an insurance policy for market changes. By designing your solution according to this methodology, your project remains flexible and is always ready for change. It is always better to correct the mistake early in the process. With this method, you keep your finger on the pulse of a dynamic market and changing user expectations. As a result, you can continuously adapt, change your strategy, and create a product that will be in demand by the target audience, even if preferences have changed during the development process. DevOps DevOps is one more way to optimize the development budget of your application. A key DevOps approach is that this practice and its culture allow team members to better interact with each other and the customer. The software development team and those responsible for the operation of the application share responsibilities clearly, and it helps you avoid shifting responsibilities from one team member to another. DevOps involves th...
Post a Comment
Read more

Abstract Factory Pattern

Abstract Factory Pattern  Gamma Categorization: Creational Design Patten Summary: When the object construction is complicated, needing multiple arguments, we should create a separate function (Factory Method) or class (Factory), which is responsible for the creation of the all object. Problem examples Suport of multiple databases Multiple data sources: Serial port, ethernet port, device driver Diferent report types Solution Abstract class Generalized interface A Factory creates instances of the concrete classes Sample Code The abstract factory public   interface   IPhotoFactory {      IAnaloguePhoto   CreateAnaloguePhoto ();      IDigitalPhoto   CreateDigitalPhoto (); } The abstract products public   interface   IAnaloguePhoto {      string   GetName (); } public   interface   IDigitalPhoto {      ...
Post a Comment
Read more

SOLID (3/5) - Liskov substitution principle

  SOLID (3/5) - Liskov substitution principle Substitutability is a principle in object-oriented programming stating that, in a computer program, if S is a subtype of T, then objects of type T may be replaced with objects of type S (i.e., an object of type T may be substituted with any object of a subtype S) without altering any of the desirable properties of the program (correctness, task performed, etc.). More formally, the Liskov substitution principle (LSP) is a particular definition of a subtyping relation, called (strong) behavioral subtyping. It is a semantic rather than merely syntactic relation, because it intends to guarantee semantic interoperability of types in a hierarchy, object types in particular. using   System ; namespace   Liskov {      public   class   Rectangle     {          //public int Width { get; set; }   ...
Post a Comment
Read more