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+# [Grouping Extension](https://github.com/wanteddev/swift-style-guide#extension%EC%9D%84-%EC%82%AC%EC%9A%A9%ED%95%98%EC%97%AC-%EC%BD%94%EB%93%9C%EB%A5%BC-%EB%85%BC%EB%A6%AC%EC%A0%81%EC%9D%B8-%EA%B8%B0%EB%8A%A5-block%EC%9C%BC%EB%A1%9C-%EB%82%98%EB%88%84%EC%96%B4%EC%A7%80%EB%8F%84%EB%A1%9D-%EA%B5%AC%EC%84%B1%ED%95%9C%EB%8B%A4)
+
+## Class
+Class는 Class Block, IBAction Block, Public Property Block, Public Method Block, Private Property Block, Private Block, Protocol Block 순으로 구분합니다.
+
+### Class Block
+* Class Block에는 초기화가 필요한 Property와 override function, 그리고 생명주기 관련된 항목을 합니다.  
+```
+
+// MARK: - Class Block
+
+final class ViewController: UIViewController {
+    @IBOutlet weak var nameLabel: UILabel!
+    private let refreshControl = UIRefreshControl()
+    private var somthingHelper: SomethingHelperProtocol?
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        // ...
+    }
+}
+
+```
+### IBAction Block
+```
+
+// MARK: - IBAction
+
+extension ViewController {
+    @IBAction func btnDidTap(_ sender: Any?) {
+        // ...
+    }
+}
+
+```
+### Public Property Block
+```
+
+// MARK: - Public Property
+
+extension ViewController {
+    var isLogin: String { 
+        // ...
+    }
+}
+
+```
+### Public Method Block
+```
+
+// MARK: - Public Method
+
+extension ViewController {
+    func publicMethod() {
+        // ...
+    }
+}
+
+```
+### Private Property Block
+```
+
+// MARK: - Private Property
+
+extension ViewController {
+    private var token: String { 
+        // ...
+    }
+}
+
+```
+### Private Method Block
+```
+
+// MARK: - Private Method
+
+extension ViewController {
+    private func privateMethod() {
+        // ...
+    }
+}
+
+```
+### Protocol Block
+```
+
+// MARK: - SomethingHelperProtocol
+
+extension ViewController: SomethingHelperProtocol {
+    func test() {
+        // ...
+    }
+}
+
+```
+## Struct
+Struct도 마찬가지로 Struct Block, Public Property Block, Public Method Block, Private Property Block, Private Block 순으로 구분합니다.
+### Struct Block
+* 초기화가 필요한 Property와 Initialization을 작성합니다.
+```
+
+// MARK: - Struct Block
+
+struct User {
+    let id: Int
+    let firstName: String
+    let lastName: String
+    let company: String?
+    
+    init(id: Int, firstName: String, lastName: String) {
+        self.id = id
+        self.firstName = firstName
+        self.lastName = lastName
+        self.company = nil
+    }
+}
+
+```
+### Public Property Block
+```
+
+// MARK: - Public Property
+
+extension User {
+    var fullName: String {
+        return firstName + lastName
+    }
+}
+
+```
+### Public Method Block
+```
+
+// MARK: - Public Method
+
+extension User {
+    func hasCompany() -> Bool {
+        return nil != company
+    }
+}
+
+```
+### Private Method Block
+```
+
+// MARK: - Private Method
+
+extension User {
+    private func friend() {
+        // ...
+    }
+}
+
+```
+## Enum
+Enum도 마찬가지로 Enum Block, Public Property Block, Public Method Block, Private Property Block, Private Block 순으로 구분합니다.
+### Enum Block
+* Enum Block은 case만 작성합니다.
+```
+
+// MARK: - Enum Block
+
+enum Region {
+    case kr
+    case jp
+    case sg
+    case hk
+    case tw
+}
+
+```
+### Public Property Block
+```
+
+// MARK: - Public Property
+
+extension Region {
+    var description: String {
+        switch self {
+        case .kr:
+            return "KR"
+        case .jp:
+            return "JP"
+        case .sg:
+            return "SG"
+        case .hk:
+            return "HK"
+        case .tw:
+            return "TW"
+        }
+    }
+}
+
+```
+### Public Method Block
+```
+
+// MARK: - Public Method
+
+extension Region {
+    func flagImage() {
+        // ...
+    }
+}
+
+```
+### Private Property Block
+```
+
+// MARK: - Private Property
+
+extension Region {
+    private var isChanged: Bool {
+        // ...
+    }
+}
+
+```
+### Private Method Block
+```
+
+// MARK: - Private Method
+
+extension Region {
+    private func imageName() {
+        // ...
+    }
+}
+
+```
+
+
+## 참고자료
+- https://gwangyonglee.tistory.com/38
+- https://www.natashatherobot.com/using-swift-extensions/
+- https://cocoacasts.com/four-clever-uses-of-swift-extensions
+- https://realm.github.io/SwiftLint/override_in_extension.html