Hi I used channels to transfer data from one application poi kotlinlang #coroutines

Hi. I used channels to transfer data from one application point to another (From one screen to another). When I call send and receive for the first time, everything works fine, but if I try to re-do send for the same channel, I can’t get the data by calling the receive method. I found a solution that needs to use consumeEach. And the truth is, if you use it, then when you re-send, the receive method returns new data. In this regard, the question is, what is the fundamental difference of consumeEach from other functions: consume, first, last and others. I give an example code

-.kt

danny

12/10/2018, 10:30 PM

Copy code

/**
 * Returns first element.
 * @throws [NoSuchElementException] if the channel is empty.
 *
 * The operation is _terminal_.
 * This function [consumes][ReceiveChannel.consume] all elements of the original [ReceiveChannel].
 *
 * **Note: This API will become obsolete in future updates with introduction of lazy asynchronous streams.**
 *           See [issue #254](<https://github.com/Kotlin/kotlinx.coroutines/issues/254>).
 */

Short version is

first

calls

consume

zak.taccardi

12/10/2018, 10:34 PM

you want to avoid closing the channel

which

.first()

will do

so future sends/offers to that channel won’t be received

it’s unfortunate that receivers of data can close the channel

goldin

12/10/2018, 10:40 PM

@zak.taccardi But consumeEach close the channel too. Why

consumeEach

work,

first

doesn’t work. I don’t understand

@danny Yea, I known, but

consumeEach

work,

first

doesn’t work.

danny

12/10/2018, 10:50 PM

first/last/others all use

consume

, so they cancel the channel -

consumeEach

iterates over the channel, so won't return until the channel is closed/cancelled

zak.taccardi

12/10/2018, 10:51 PM

use

for( item in channel)

to avoid closing the channel on unsubscription

goldin

12/10/2018, 11:22 PM

@zak.taccardi Hm….. I always send only one number. If use

for( item in channel)

this, it will be at least strange to do a search from a single element.

Maybe there is another way to apply events?

uli

12/11/2018, 5:38 AM

Just use receive

goldin

12/11/2018, 7:02 AM

@uli

receive

not get result when channel out of capacity. my capacity equal 1.

Daniel Tam

12/11/2018, 1:27 PM

*capacity you mean?

goldin

12/11/2018, 1:48 PM

@Daniel Tam yes

uli

12/11/2018, 6:45 PM

So you write more then you consume?

zak.taccardi

12/11/2018, 6:45 PM

Use an unlimited capacity then

uli

12/11/2018, 6:46 PM

You write you always send one number only. So capacity of one should never get exceeded

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