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# waitUntilCompleted()

Waits until the [`CIRenderTask`](/documentation/CoreImage/CIRenderTask) finishes and returns.

```
func waitUntilCompleted() throws -> CIRenderInfo
```

## Discussion

Synchronously blocks execution until the [`CIRenderTask`](/documentation/CoreImage/CIRenderTask) either completes or fails (with error).  Calling this method after [`startTask(toRender:to:)`](/documentation/CoreImage/CIContext/startTask(toRender:to:)) or [`startTask(toRender:from:to:at:)`](/documentation/CoreImage/CIContext/startTask(toRender:from:to:at:)) makes the render task behave synchronously, as if the CPU and GPU were operating as a single unit.

---

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