A project to demonstrate the use of kotlin flows, channels, and other components of Coroutines
The send() function in Channel is suspending. The reasoning behind this is that you may want to pause the code that is sending elements until there is someone actually listening for the data. This concept is often referred to as backpressure, and helps to prevent your channels from being flooded with more elements than the receivers can actually process.
In order to configure this backpressure, you can define a buffer for your channel. The coroutine sending data through the channel will be suspended when the elements in the channel have reached the size of the buffer. Once elements are removed from the channel, the sender will be resumed.
- Rendezvous Channel
- Conflated Channel
- Buffered
- Unlimited
- offer() adds the object to the channel if there is room in its buffer and returns true, otherwise it returns false
- send() adds the object to the channel if there is room in its buffer and suspends otherwise until there is room
send() suspends, it has the suspend keyword and must be called inside of a coroutine. offer() does not suspend and can be called from normal functions, but you need to deal with the case where it returns false. Here, “deal with” could simply mean “ignore the return value and do not worry about the case where the offer was not accepted”
You can proactively close a SendChannel by calling close(). A holder of a SendChannel can see if it is closed via isClosedForSend(), while the holder of a ReceiveChannel can see if it is closed via isClosedForReceive(). Iterating consumers, such as consumeEach(), automatically check for closure and will handle that accordingly — in the case of consumeEach(), it returns.
There are other “terminal operators” besides consumeEach() for getting data off of a ReceiveChannel
- offer() is a regular (non-suspend) function that puts an object into the channel if there is room
- poll() is a regular (non-suspend) function that takes an object out of the channel if there is one, returning null otherwise