শুক্রবার, ১৫ নভেম্বর, ২০১৩

SOLID Principles Overview



  •   GB article G real world example w`‡q SOLID principle explain Ki‡ev|

  • SOLID principles n‡”Q cuvPwU programming principles hvnv mKj well designed application Gi foundation wnmv‡e consider Kiv nq|

  • GB principle mg~n e¨envi K‡i easy to extend I maintainable application ‰Zix Ki‡Z e¨eüZ nq|


  •  GLb Avgiv principle mg~n wb‡q Av‡jvPbv Ki‡ev|

  • cÖ_‡g Avgiv D³ principle mg~‡ni acronym define Ki‡ev:

S: Single Responsibility Principle -- GKwU class/Modules/Functions change  Gi Rb¨ GKwU gvÎ reason _vK‡e.
O: Open/Closed Principle – Classes/Functions/Modules  mg~n extension Gi Rb¨ open _vK‡e wKš‘ modification Gi Rb¨ closed _vK‡e.
L: Liskov Substitution Principle -- Derived class ‡K base class Gi cwie‡Z© e¨envi Kiv hv‡e|
I: Interface Segregation Principle – Larger interface Gi AcÖ‡qvRbxq member mg~n implement Kivi Rb¨ Clients   †K  force Kiv hv‡e bv ZvB larger interface ‡K †f‡½ Smaller I Consistent interface G fvM Ki‡Z n‡e|
D: Dependency Inversion Principle – Top level class mg~n Ges bottom level class mg~n G‡K Ac‡ii Dci dependent _v‡K bv| Df‡q Abstraction Gi gva¨‡g G‡K Ac‡ii mv‡_ Connected nq A_©vr Top level I bottom level class mg~n Abstraction/Interface Gi Dci dependent _vK‡e|
  • We will be working with a Web application that searches a database for documents that match very simple criteria:
  • Avgiv GKwU Web application Gi search method wb‡q Av‡jvPbv Ki‡ev |
  • GB search method G Avgiv data search Kivi Rb¨ database G search Ki‡ev| GB search method wb‡¤œv³ criteria mg~n Øviv database G search Ki‡e-
    • First name,
    • Last name and
    • Account number  hvnv Aek¨B user enters character Øviv Start n‡e|
  • wb‡¤œ search screen ‡`qv n‡jv-










Search button Gi code wb‡¤œ †`qv n‡jv (Bnv refactoring version  bv)-
protected void BtnSearch_Click(object sender, EventArgs e)
{
    var sbCriteria = new StringBuilder();
    using (var db = new SolidDemoEntities())
    {
        var query = db.Documents.AsQueryable();
        if (!String.IsNullOrWhiteSpace(TxbAccount.Text))
        {
            query = query.Where(d => d.Account.StartsWith(TxbAccount.Text));
            sbCriteria.AppendFormat("Account starts with '{0}' AND ", TxbAccount.Text);
        }

        if (!String.IsNullOrWhiteSpace(TxbLastName.Text))
        {
            query = query.Where(d => d.LastName.StartsWith(TxbLastName.Text));
            sbCriteria.AppendFormat("Last Name starts with '{0}' AND ", TxbLastName.Text);
        }

        if (!String.IsNullOrWhiteSpace(TxbFirstName.Text))
        {
            query = query.Where(d => d.FirstName.StartsWith(TxbFirstName.Text));
            sbCriteria.AppendFormat("First Name starts with '{0}' AND ", TxbFirstName.Text);
        }

        if (sbCriteria.Length > 5)
            sbCriteria.Remove(sbCriteria.Length - 5, 5);
        else
            sbCriteria.Append("-- all records --");

        LblCriteria.Text = sbCriteria.ToString();

        LvwResults.DataSource = query.ToArray();
        LvwResults.DataBind();
    }
}
  • Dc‡iv³ coding style Single Responsibility Principle ‡K violate K‡i KviY-
    • mKj responsibility mg~n GKwU button click Gi against G handle Kiv nq-
    • wb‡¤œ handled responsibility mg~n cÖ`Ë n‡jv-
      • User's input parse K‡i|
      • Database connection Manage K‡i|
      • Database query build K‡i (string AvKv‡i Ges LINQ Expression AvKv‡i)
      • Query Execute K‡i|
      • Result mg~n form G Bind K‡i|
      • GgbwK Bnv‡Z †Kvb error-handling bvB|
  • Dc‡iv³ approach bad ‡Kb?
  • mKj code GKwU place G ivLv n‡q‡Q
  • hZÿY GKwU application ‡QvU _v‡K ZZÿY Bnv mgm¨v bv|
  • Application  hw` Large nq Ges cÖwZwU pages G multiple actions _v‡K Z‡e GB approach Gi wKQz drawbacks _v‡K|
  • wb‡¤œ KwZcq drawbacks D‡jøL Kiv n‡jv-
ü  Application Gi unit-test possible bv|
ü  Bnv ZLbB KvR Ki‡e hLb ASP.NET context G run Ki‡e|
ü  Bnv database presence expect Ki‡e|
ü  †Kvb can reuse Kiv hv‡e bv|
  • d‡j Avgiv hw` more features add Ki‡Z PvB (D`vniY ¯^iƒc audit  Gi Rb¨ search log manage Kiv) Z‡e D³ logging  Gi Rb¨ †h coding  Ki‡Z n‡e ZvnvI same method G Ki‡Z n‡e|
  • †m‡ÿ‡Î existing trusted code modify Ki‡Z n‡e|
  • Existing trusted code modify  Ki‡j wb‡¤œv³ Problem mg~n raise Ki‡Z cv‡i-
    • Existing code G bug introduce n‡Z cv‡i|
    • Unit Testing complex n‡q hv‡e|
    • Code maintainability lose Ki‡e|
    • Multiple logic handle Kivi Kvi‡Y method Gi complexity raise Ki‡e|
    • Readability K‡g hv‡e|
    • Reusability K‡g hv‡e|
    • GQvov Av‡iv A‡bK ..
  • Dc‡iv³ Problem mg~n Overcome Kivi Rb¨B Avgiv SOLID Principle use Ki‡ev|


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