Hi guys, I am doing baby step on

Channel

Buffer. I am learning to Poll item through

Channel

. When I send item, it doesn't

receive()

all item. I don't understand why?

You don’t explicitly “poll” a Channel. Simply using its Iterator

for element in basketChannel

will react once an item is sent to the channel. It’s a push-based mechanism, where items that are sent to the channel cause the receiver to react to the item, as opposed to a “poll” which is a pull-based mechanism The additional

basketChannel.receive

will cause the channel to consume an additional item, effectively consuming 2 items for every 1 iteration, basically dropping every other item in your case (or suspending indefinitely if you do not send an even number of items)

remove the receive call from the startPolling method

So How can I use pull base mechanism. Actually I want to queue the Item, if something is processng.

the next element won't be removed from the queue until a single iteration of that

for

body is complete.

Okk, then I'll remove the

for

. from the startPolling

When someone calls

channel.send()

or

channel.trySend()

, an item gets placed into a queue within the channel. That item will stay within that queue until somewhere else, something starts reading from the channel. There are several ways to read values from the channel: You can implement your own loop and manually call

receive()

within the loop:

while(true) {
    val item = channel.receive()
    handleItem(item) 
}

You can use the Channels Iterator

for(item in channel) {
    handleItem(item) 
}

You can receive the items as a Flow:

channel
    .receiveAsFlow()
    .onEach { handleItem(it) }
    .launchIn(viewModelScope)

All of these mechanisms effectively do the same thing: read items one at a time from the Channel’s queue, suspending until new items are sent. However, they’re not perfectly equivalent. Most notably, the first example (directly calling

channel.receive()

) will throw an exception once the channel is closed, while the other two mechanisms (iterator and Flow), will simply stop sending items without throwing an exception. This is why we’re recommending using the Iterator rather than calling

channel.receive()

, because it’s more natural to how you would typically use a Channel and you don’t need to worry about handling exceptions

Thank you so much for great explanation. I'll keep in mind what you just mention.