Added SRP example code

Author: Sebastian Boldt

GOFSwift.xcworkspace/xcuserdata/sboldt.xcuserdatad/UserInterfaceState.xcuserstate

@@ -63,7 +63,7 @@
 
 ✅ Dependency Inversion Principle (DIP)
 
-❌ Single Responsibilty Principle  (SRP)
+✅ Single Responsibilty Principle  (SRP)
 
 ❌ Open Closed Principle (OCP)
 

README.md

@@ -2,6 +2,11 @@
 
 import Foundation
 
+/*
+ A. HIGH LEVEL MODULES SHOULD NOT DEPEND UPON LOW LEVEL MODULES. BOTH SHOULD DEPEND UPON ABSTRACTIONS.
+ B. ABSTRACTIONS SHOULD NOT DEPEND UPON DETAILS. DETAILS SHOULD DEPEND UPON ABSTRACTIONS.
+*/
+
 // The Problem - Tightly coupled classes
 
 struct Wrong {

SOLID.playground/Pages/Dependency Inversion.xcplaygroundpage/Contents.swift

@@ -2,6 +2,6 @@
 
 import Foundation
 
-var str = "Hello, playground"
+// SOFTWARE ENTITIES (CLASSES, MODULES, FUNCTIONS, ETC.) SHOULD BE OPEN FOR EXTENSION, BUT CLOSED FOR MODIFICATION.
 
 //: [Next](@next)

SOLID.playground/Pages/Open Closes Principle.xcplaygroundpage/Contents.swift

@@ -2,4 +2,71 @@
 
 import UIKit
 
-var str = "Hello, playground"
+// THERE SHOULD NEVER BE MORE THAN ONE REASON FOR A CLASS TO CHANGE.
+
+struct Wrong {
+    class APIHandler {
+        func handle() {
+            let data = requestDataFromAPI()
+            let array = parse(data: data)
+            saveToDB(array: array)
+        }
+        
+        private func requestDataFromAPI() -> Data {
+            // send API request and wait the response
+            return Data()
+        }
+        
+        private func parse(data: Data) -> [String] {
+            // parse the data and create the array
+            return []
+        }
+        
+        private func saveToDB(array: [String]) {
+            // save the array in a database (CoreData/Realm/...)
+        }
+    }
+}
+
+//TODO: We should use the Dependency Inversion here too ...
+
+struct Right {
+    class APIHandler {
+        let requestHandler: RequestHandler
+        let parseHandler: ParseHandler
+        let dbHandler: DataBaseHandler
+        
+        init(requestHandler: RequestHandler, parseHandler: ParseHandler, dbHandler: DataBaseHandler) {
+            self.requestHandler = requestHandler
+            self.parseHandler = parseHandler
+            self.dbHandler = dbHandler
+        }
+        
+        func handle() {
+            let data = requestHandler.requestDataFromAPI()
+            let array = parseHandler.parse(data: data)
+            dbHandler.saveToDB(array: array)
+        }
+    }
+    
+    class RequestHandler {
+        func requestDataFromAPI() -> Data {
+            // send API request and wait the response
+            return Data()
+        }
+    }
+    
+    class ParseHandler {
+        func parse(data: Data) -> [String] {
+            // parse the data and create the array
+            return []
+        }
+    }
+    
+    class DataBaseHandler {
+        func saveToDB(array: [String]) {
+            // save the array in a database (CoreData/Realm/...)
+        }
+    }
+}
+