当时无法订阅 [英] Failed to subscribe thenMany item

问题描述

当我使用Mono.thenMany时，通量数据丢失了，为什么?

When I use Mono.thenMany, the Flux data is lost, why?

@Test
fun thenManyLostFluxDataTest() {
  Mono.empty<Int>()
    .thenMany<Int> { Flux.fromIterable(listOf(1, 2)) }
    .subscribe { println(it) } // why not output item 1, 2
}

如果我更改为使用blockLast()进行订阅，则测试方法将永远运行.太可怕了:

If I change to use blockLast() to do the subscribe, the test method run forever. So fearful:

@Test
fun thenManyRunForeverTest() {
  Mono.empty<Int>()
    .thenMany<Int> { Flux.fromIterable(listOf(1, 2)) }
    .blockLast() // why run forever
}

现在，我使用另一种方法来执行thenMany方法应做的事情:

Now I use another way to do what the thenMany method should do:

// this method output item 1, 2
@Test
fun flatMapIterableTest() {
  Mono.empty<Int>()
    .then(Mono.just(listOf(1, 2)))
    .flatMapIterable { it.asIterable() }
    .subscribe { println(it) } // output item 1, 2 correctly
}ed

推荐答案

您正在使用Kotlin的"lambda作为最后一个参数"的简短语法.问题是，如果您查看thenMany方法签名，则它不接受Function，而是接受Publisher.

You are using Kotlin's "lambda as a last parameter" short-form syntax. The thing is, if you look at the thenMany method signature, it doesn't accept a Function, but a Publisher.

那么为什么lambda被接受，它代表什么呢?

So why is that lambda accepted, and what does it represent?

实际上它似乎被解释为Publisher(因为它只有1种方法，subscribe(Subscriber))！

It seems to be in fact interpreted as a Publisher (as it has only 1 method, subscribe(Subscriber))!

将{ }替换为( )，一切将恢复正常.

Replace the { } with ( ) and everything will be back to normal.

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