Factory Design Pattern

Introduction

Factory design pattern is most common creational pattern. In Factory pattern, we create object without exposing the creation logic to the client and refer to newly created object using a common interface.

When we use

Factory pattern can come in handy when you want to reduce the dependency of a class on other classes. On the other hand, it encapsulates the object creation process and users can simply pass in parameters to a generic factory class without knowing how the objects are actually being created. Also it gives you a clean code.

How to use

For factory pattern we need 3 components.

Base class like shape In swift , we use protocol to implement factory design pattern.
subclasses of base like triangle , square, we can make class of protocol
Decision making class where we check parameter and take decision to create appropriate object of base class from child class and return to caller

Example of Factory pattern

For creation design pattern:

First create the base protocol for general definition of class .

//MARK: - URL Body Protocol
 protocol URLBodyProtocol : class {
    func getSyncDataInJson(fromDataObject dataObject : Any) -> JSON

 }

Make subclasses of base class.

GPS Body paramter sub class

class GPSBodyParameter : URLBodyProtocol {
    func getSyncDataInJson(fromDataObject dataObject: Any) -> JSON {
     // Custom implementation
   }
 }

Health Form paramter sub class

 class HealthFormBodyParameter : URLBodyProtocol {
    func getSyncDataInJson(fromDataObject dataObject: Any) -> JSON {
 // Custom implementation

    }
}

Safety Form paramter sub class

 class SafetyFormBodyParameter : URLBodyProtocol {
    func getSyncDataInJson(fromDataObject dataObject: Any) -> JSON {
 // Custom implementation

   }
}

Make choice enum

  public enum syncDataType: String {

case gpsMobileLocation = "Mobile GPS Location Data"
case healthForm = "Mobile Health Form Submissions"
case safetyForm = "Mobile Safety Form Submissions"

}

Now the Decesion making class

class URLBodyHandler {

  static func  getBodyParamter(ofType syncType : String) -> String {

    let  urlBodyProtocol : URLBodyProtocol?

    if syncType == syncDataType.gpsMobileLocation.rawValue {
        urlBodyProtocol = GPSBodyParameter()
    } else if syncType == syncDataType.healthForm.rawValue {
        urlBodyProtocol = HealthFormBodyParameter()
    } else if syncType == syncDataType.safetyForm.rawValue {
        urlBodyProtocol = SafetyFormBodyParameter()
    } 

    }
    // let gpsBodyParameter : GPSBodyParameter = GPSBodyParameter()
    return urlBodyProtocol!.getBodyString(ofType: syncType, fromDataObject: syncDataObject)

   }
}

And to call this function ti get dynamic subclass at run time

 let gpsformString =  URLBodyHandler.getBodyParamter(ofType: syncDataType.gpsMobileLocation.rawValue)

Factory Design Pattern