সোমবার, ১৮ নভেম্বর, ২০১৩

Lazy Load Pattern




  • Lazy Load Pattern use K‡i GKwU Object ‡K on Demand load/ initialize Kiv nq| 
  • Ab¨fv‡e ejv hvq hLb cª‡qvRb ZLb loading Gi gva¨‡g object creation defer Kiv nq| 

UML Diagram:



Benefits

  • hvnv cÖ‡qvRb ïaygvÎ Zvnv loading Gi gva¨‡g memory Save Kiv nq|
  • Execution deferring Gi gva¨‡g initial load time reduce Kiv nq|
Drawbacks:
  • lazy-loading Gi gva¨‡g load K…Z object wUi first time load delay n‡Z cv‡i|
Description:
·         Lazy-loading ORMs (Object-relational mappings) Gi key feature.
·         KviY ORM ZLbB database query ‡Z perform K‡i hLb data required nq| d‡j data retrieval time reduce nq|

Code Examples:
  • g‡bKwi Avgv‡`i `ywU class Av‡Q Candidate class I EducationProfile class. 
  • GKRb candidate Gi GKvwaK EducationProfile(like: Bachelors (BBA) ,Master(MBA)) Av‡Q| 
  • GLb Avgiv candidate Gi mv‡_ Zvi Education Profile load Kiv‡Z PvB  Z‡e Candidate Gi mv‡_ associated EducationProfiles load Ki‡Z n‡e| †m‡ÿ‡Î Candidate object initialize Ki‡Z n‡e| d‡j A‡bK fvix n‡q hv‡e| 
  • GB situation avoid Kivi Rb¨ Avgiv Lazy Loading Pattern use Ki‡ev| 
  • G‡ÿ‡Î ZLbB EdutioanProfile load n‡e hLb EducationProfile list use Kiv n‡e| 
  • d‡j data retrieval faster n‡e Ges performance increase n‡e| 
  • bx‡P Candidate EducationProfile load Gi Rb¨ Lazy loading pattern define Kiv n‡jv- 
  • cÖ_‡g Avgiv Candidate I EducationProfile class Øq create Ki‡ev-
public class EducationProfile
{
    public int Id { get; set; }
    public string Digree { get; set; }
    public DateTime PassingYear { get; set; }
}

//Hope this will give you a little reference of lazy loading

public class Candiate
{
    public string Name { get; set; }
    public int EducationProfileId { get; set; }
    public List GetAllEducationProfile()
    {
        return educationProileList.value;
    }

    Lazy<list<educationproile>> educationProileList;

    public Candiate(string name, int id)
    {
        //Initializing Candiate Object
        Name = name;
        EducationProfileId = id;
        educationProileList = new Lazy<list<educationproile>>(() => { return GetEducationProfileList(id); });
        //Initialization done
    }

    private List GetEducationProfileList(int id)
    {
        //Loading EducationProiles
        List list = new List();
        Parallel.For(100, 110, (int i) =>
        {
            EducationProile educationprofile = new EducationProile();
            educationprofile.Id = i;
            list.Add(educationprofile);
        });
        return list;
    }
}
</list<educationproile></list<educationproile>
·         Candidate class Gi constructor Gi g‡a¨ properties mg~n initialize Kiv n‡q‡Q Ges educationProileList object declare Kiv n‡q‡Q| (educationProileList GKwU generic List Ges Bnv‡K GetEducationProfileList method Øviv fill Kiv n‡q‡Q)
·         GB method ZLbB call Kiv n‡e hLb educationProileList object use n‡e|
·         wb‡¤œ main method define Kiv n‡q‡Q hvnv lazy loading Gi behavior show K‡i-
public static void Main(string[] args)
{
    Candidate candidate = new Candidate("AnyName", 1);
    foreach(EducationProile eduProfile in candiate.GetAllEducationProfile())
    // it will actually load accounts, ie. lazy loading
    Console.WriteLine("Id:{0}",eduProfile.Id);
    Console.Read();
}
When to Use
wb‡¤œ KwZcq situation ‡`qv n‡jv †h‡ÿ‡Î Lazy-loading pattern use Ki‡j effective result cvIqv hvq-
  • GKwU tab widget Gi content mg~n ZLbB load n‡e hLb D³ tab Dnv‡`i show Ki‡e
  • GKwU image gallery ZLbB image mg~n load Ki‡e hLb D³ gallery Gi image mg~n viewed n‡e
 





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