How to pause operation queue in Swift

Question

I have a couple of operations to perform on the IoT device from iOS App. So All my operations are in OperationsQueue with serial operations.

Here I want to perform one operation at a time and each operation needs to wait until I get a response from the IoT device.

Here IoT device response will take time to send back. so how to wait for the current operation in operation queue until I get a response from IoT.

So is there any way to pause current running operation until getting a response from IoT and then I will resume it so that the next operation in operation queue will start.

I tried with Sleep operation But it required time, but we can not guarantee about IoT device response.

Any suggestions would appreciate it. Thank you in advance.

Answer 1

The basic idea is that you don’t pause (or wait, or sleep), but rather you define a “concurrent” operation (see discussion of concurrent operations in the documentation) that doesn’t trigger the isFinished KVO until the device responds.

A simple way to do this is to write a concurrent operation class, like the one shown in this answer. Then your IoT operation can subclass that AsynchronousOperation class, and just call finish() when the device responds.

Then your operation queue (which presumably has a maxConcurrentOperationCount of 1, or perhaps is using dependencies), will not start an operation until the prior operation has finished.