# addPresentedHandler(_:) Registers a block of code to be called immediately after the drawable is presented. ``` func addPresentedHandler(_ block: @escaping MTLDrawablePresentedHandler) ``` ## Parameters `block` A block of code to be invoked. ## Discussion You can register multiple handlers for a single drawable object. The following example code schedules a presentation handler that reads the [`presentedTime`](/documentation/Metal/MTLDrawable/presentedTime) property and uses it to derive the interval between the last and current presentation times. From that information, it determines the app’s frame rate. ```objective-c // Property declarations @property (nonatomic) CFTimeInterval previousPresentedTime; /* ... */ // Render loop __block Renderer *strongSelf = self; [view.currentDrawable addPresentedHandler:^(id drawable) { CFTimeInterval presentationDuration = drawable.presentedTime - strongSelf.previousPresentedTime; CFTimeInterval frameRate = 1.0/presentationDuration; /* ... */ strongSelf.previousPresentedTime = drawable.presentedTime; }]; ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)