diff --git a/Example/Tests/IntegratedTest.swift b/Example/Tests/IntegratedTest.swift
index 5026f29..72b91f9 100644
--- a/Example/Tests/IntegratedTest.swift
+++ b/Example/Tests/IntegratedTest.swift
@@ -113,6 +113,81 @@ class IntegratedTestSpec: QuickSpec {
             }
             expect(sResult.isSucceed).to(beTrue())
         }
+        it("should invoke observer method") {
+            let randomNumber: Int = .random(in: 0..<10)
+            var requestResult: URLResult?
+            var observer: SpyObserver<URLResult>!
+            let request = Ness(onDuplicated: .keepAllCompletion)
+                .httpRequest(.get, withUrl: "https://jsonplaceholder.typicode.com/todos/\(randomNumber)")
+                .prepareDataRequest(with: CounterRetryControl(maxRetryCount: 3))
+                .validate(statusCodes: 200..<300)
+            waitUntil(timeout: .seconds(15)) { done in
+                observer = SpyObserver { result in
+                    requestResult = result
+                    done()
+                }
+                request.then(observing: observer, call: SpyObserver.invoke(with:))
+            }
+            guard let result = requestResult else {
+                fail("Fail to get data")
+                return
+            }
+            expect(result.isSucceed).to(beTrue())
+        }
+        it("should invoke one of observer method") {
+            let randomNumber: Int = .random(in: 0..<10)
+            var requestResult: URLResult?
+            var observer: SpyObserver<URLResult>!
+            let request = Ness(onDuplicated: .keepAllCompletion)
+                .httpRequest(.get, withUrl: "https://jsonplaceholder.typicode.com/todos/\(randomNumber)")
+                .prepareDataRequest(with: CounterRetryControl(maxRetryCount: 3))
+                .validate(statusCodes: 200..<300)
+            waitUntil(timeout: .seconds(15)) { done in
+                observer = SpyObserver { result in
+                    requestResult = result
+                    done()
+                }
+                request.then(
+                    observing: observer,
+                    call: SpyObserver.invoke(with:),
+                    whenFailedCall: SpyObserver.invoke(with:)
+                )
+            }
+            guard let result = requestResult else {
+                fail("Fail to get data")
+                return
+            }
+            expect(result.isSucceed).to(beTrue())
+        }
+        it("should invoke observer method twice") {
+            let randomNumber: Int = .random(in: 0..<10)
+            var requestResult: URLResult?
+            var observer: SpyObserver<URLResult>!
+            let request = Ness(onDuplicated: .keepAllCompletion)
+                .httpRequest(.get, withUrl: "https://jsonplaceholder.typicode.com/todos/\(randomNumber)")
+                .prepareDataRequest(with: CounterRetryControl(maxRetryCount: 3))
+                .validate(statusCodes: 200..<300)
+            waitUntil(timeout: .seconds(15)) { done in
+                observer = SpyObserver { result in
+                    requestResult = result
+                    if observer.invokedTime == 2 {
+                        done()
+                    }
+                }
+                request.then(
+                    observing: observer,
+                    call: SpyObserver.invoke(with:),
+                    whenFailedCall: SpyObserver.invoke(with:),
+                    finallyCall: SpyObserver.invoke(with:)
+                )
+            }
+            guard let result = requestResult else {
+                fail("Fail to get data")
+                return
+            }
+            expect(result.isSucceed).to(beTrue())
+            expect(observer.invokedTime).toEventually(equal(2))
+        }
         it("should get json data") {
             let randomNumber: Int = .random(in: 40..<50)
             var requestResult: URLResult?
diff --git a/Example/Tests/Mock.swift b/Example/Tests/Mock.swift
index 287109e..f950c76 100644
--- a/Example/Tests/Mock.swift
+++ b/Example/Tests/Mock.swift
@@ -55,3 +55,15 @@ extension String {
         return randomString
     }
 }
+
+class SpyObserver<Result> {
+    var invokedTime: Int = 0
+    let invoked: (Result) -> Void
+    init(_ invoked: @escaping (Result) -> Void) {
+        self.invoked = invoked
+    }
+    func invoke(with result: Result) {
+        invokedTime += 1
+        invoked(result)
+    }
+}
diff --git a/README.md b/README.md
index 344c150..50aa364 100644
--- a/README.md
+++ b/README.md
@@ -91,16 +91,17 @@ Ness.default
     .executeAndForget()
 ```
 
-you can do something very readable like this by separating all closure using function:
+you can do something very readable like this by using observer method call:
 
 ```swift
 Ness.default
     .httpRequest(.get, withUrl: "https://myurl.com")
     .prepareDataRequest()
     .then(
-        run: updateTheViewWithData,
-        whenFailed: showFailureAlert,
-        finally: removeLoading
+        observing: self,
+        call: Some.updateTheView(withResult:),
+        whenFailedCall: Some.showFailureAlert,
+        finallyCall: Some.removeLoading
     )
 ```
 
@@ -269,7 +270,24 @@ Ness.default
     )
 ```
 
-With custom dispatcher which will be the thread where completion run:
+You could do something similar with observer and its method reference. It will be weak refer to observer and do nothing if the observer is already deinitialised by ARC:
+```swift
+Ness.default
+    .httpRequest(.get, withUrl: "https://myurl.com")
+    ..
+    ..
+    .prepareDataRequest()
+    .then(
+        observing: self,
+        call: Some.updateTheView(withResult:),
+        whenFailedCall: Some.showFailureAlert,
+        finallyCall: Some.removeLoading
+    )
+```
+
+All of the complement method (whenFailedCall, finallyCall) are optional. Use it when you need it.
+
+You could give custom dispatcher which will be the thread where completion run:
 
 ```swift
 Ness.default
diff --git a/iONess.podspec b/iONess.podspec
index 2a77fd1..fc482b6 100644
--- a/iONess.podspec
+++ b/iONess.podspec
@@ -8,7 +8,7 @@
 
 Pod::Spec.new do |s|
   s.name             = 'iONess'
-  s.version          = '1.2.2'
+  s.version          = '1.2.3'
   s.summary          = 'iOS Network Session'
 
 # This description is used to generate tags and improve search results.
diff --git a/iONess/Classes/DropableAndResumable/DropableURLRequest.swift b/iONess/Classes/DropableAndResumable/DropableURLRequest.swift
index d56a617..6fb47b7 100644
--- a/iONess/Classes/DropableAndResumable/DropableURLRequest.swift
+++ b/iONess/Classes/DropableAndResumable/DropableURLRequest.swift
@@ -77,7 +77,8 @@ extension BaseDropableURLRequest {
         ) { retryStatus in
             switch retryStatus {
             case .retryAfter(let delay):
-                DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: onRetry)
+                let dispatcher: DispatchQueue = OperationQueue.current?.underlyingQueue ?? .main
+                dispatcher.asyncAfter(deadline: .now() + delay, execute: onRetry)
             case .retry:
                 onRetry()
             case .noRetry:
diff --git a/iONess/Classes/Thenable/Thenable.swift b/iONess/Classes/Thenable/Thenable.swift
index fd67804..3d6776d 100644
--- a/iONess/Classes/Thenable/Thenable.swift
+++ b/iONess/Classes/Thenable/Thenable.swift
@@ -32,6 +32,31 @@ public protocol Thenable {
     ///   - deferClosure: closure which will be run after closure or failClosure
     @discardableResult
     func then(run closure: @escaping (Result) -> Void, whenFailed failClosure: @escaping (Result) -> Void, finally deferClosure: @escaping (Result) -> Void) -> DropablePromise
+    
+    
+    /// Method to execute request and then run any method passed
+    /// - Parameters:
+    ///   - observer: object that observe request
+    ///   - method: observer method to call when request completed
+    @discardableResult
+    func then<Observer: AnyObject>(observing observer: Observer, call method: @escaping (Observer) -> ((Result) -> Void)) -> DropablePromise
+    
+    /// Method to execute request and then run any method passed
+    /// - Parameters:
+    ///   - observer: object that observe request
+    ///   - method: observer method to call when succeed
+    ///   - failMethod: observer method to call when fail
+    @discardableResult
+    func then<Observer: AnyObject>(observing observer: Observer, call method: @escaping (Observer) -> ((Result) -> Void), whenFailedCall failMethod: @escaping (Observer) -> ((Result) -> Void)) -> DropablePromise
+    
+    /// Method to execute request and then run any method passed
+    /// - Parameters:
+    ///   - observer: object that observe request
+    ///   - method: observer method to call when succeed
+    ///   - failMethod: observer method to call when fail
+    ///   - finalMethod: observer method to call when request completed
+    @discardableResult
+    func then<Observer: AnyObject>(observing observer: Observer, call method: @escaping (Observer) -> ((Result) -> Void), whenFailedCall failMethod: @escaping (Observer) -> ((Result) -> Void), finallyCall finalMethod: @escaping (Observer) -> ((Result) -> Void)) -> DropablePromise
 }
 
 public extension Thenable {
@@ -54,4 +79,55 @@ public extension Thenable {
             }
         )
     }
+    
+    /// Method to execute request and then run any method passed
+    /// - Parameters:
+    ///   - observer: object that observe task
+    ///   - method: observer method to call when task completed
+    /// - Returns: DropablePromise object
+    @discardableResult
+    func then<Observer: AnyObject>(observing observer: Observer, call method: @escaping (Observer) -> ((Result) -> Void)) -> DropablePromise {
+        return then { [weak observer] result in
+            guard let observer = observer else { return }
+            method(observer)(result)
+        }
+    }
+    
+    /// Method to execute request and then run any method passed
+    /// - Parameters:
+    ///   - observer: object that observe task
+    ///   - method: observer method to call when succeed
+    ///   - failMethod: observer method to call when fail
+    /// - Returns: DropablePromise object
+    @discardableResult
+    func then<Observer: AnyObject>(observing observer: Observer, call method: @escaping (Observer) -> ((Result) -> Void), whenFailedCall failMethod: @escaping (Observer) -> ((Result) -> Void)) -> DropablePromise {
+        return then(run: { [weak observer] result in
+            guard let observer = observer else { return }
+            method(observer)(result)
+        }, whenFailed: { [weak observer] result in
+            guard let observer = observer else { return }
+            failMethod(observer)(result)
+        })
+    }
+    
+    /// Method to execute request and then run any method passed
+    /// - Parameters:
+    ///   - observer: object that observe task
+    ///   - method: observer method to call when succeed
+    ///   - failMethod: observer method to call when fail
+    ///   - finalMethod: observer method to call when task completed
+    /// - Returns: DropablePromise object
+    @discardableResult
+    func then<Observer: AnyObject>(observing observer: Observer, call method: @escaping (Observer) -> ((Result) -> Void), whenFailedCall failMethod: @escaping (Observer) -> ((Result) -> Void), finallyCall finalMethod: @escaping (Observer) -> ((Result) -> Void)) -> DropablePromise {
+        return then(run: { [weak observer] result in
+            guard let observer = observer else { return }
+            method(observer)(result)
+        }, whenFailed: { [weak observer] result in
+            guard let observer = observer else { return }
+            failMethod(observer)(result)
+        }, finally: { [weak observer] result in
+            guard let observer = observer else { return }
+            finalMethod(observer)(result)
+        })
+    }
 }