Hi. I used channels to transfer data from one appl...

# coroutines

[goldin]

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]

/**
 * 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>).
 */

[danny]

Short version is first calls consume

[zak.taccardi]

you want to avoid closing the channel

[zak.taccardi]

which .first() will do

[zak.taccardi]

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

[zak.taccardi]

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

[goldin]

@zak.taccardi But consumeEach close the channel too. Why consumeEach work, first doesn’t work. I don’t understand

[goldin]

@danny Yea, I known, but consumeEach work, first doesn’t work.

[danny]

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]

use for( item in channel) to avoid closing the channel on unsubscription

[goldin]

@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.

[goldin]

Maybe there is another way to apply events?

[uli]

Just use receive

[goldin]

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

[Daniel Tam]

*capacity you mean?

[goldin]

@Daniel Tam yes

[uli]

So you write more then you consume?

[zak.taccardi]

Use an unlimited capacity then

[uli]

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