Kotlin inner list filtering

Question

I have a list like below,

ThreadsList-
    Thread1-
       Messages-
         Message1
           text="@"
         Message2
           text="hello"
    Thread2-
       Messages-
         Message1
           text="@"
         Message2
           text="hello"
         Message3
           text="hi"

I need to remove all messages inside each Thread that has the text "@"

I have tried the below code but it's not working as expected,

threadsList.filter { item ->
            item.messages.any { !it.text.equals("@")  }
        }

use Messages1 instead of any.

Mustafo aka Shokhrukh Makmudov
– Mustafo aka Shokhrukh Makmudov

2021-02-11 08:12:53 +00:00
Commented Feb 11, 2021 at 8:12 — Mustafo aka Shokhrukh Makmudov
– Mustafo aka Shokhrukh Makmudov, Commented Feb 11, 2021 at 8:12

Antonio · Accepted Answer · 2021-02-11 08:24:08Z

1

What you have done by your code is to filter out the threads that contains all messages with text @. Since you have applied the filter method on threadsList, you will get a output threadsList in which all threads contains at least a non-@ message.

Now, what you have to do is perform some operation on all threads in the threadsList to filter out the messages with @ in it. It looks like this :

threadsList.onEach { thread ->
            thread.messages.filter { message ->
                message.text != "@"
            }
        }

and this will returned a threadsList which you need.

answered Feb 11, 2021 at 8:24

Antonio

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Tarmo · Accepted Answer · 2021-02-11 10:19:16Z

1

It's a bit hard to be sure without seeing what kind of classes you use, but assuming you use data classes, it can be done similarly to this:

val cleanThreadList = threadList.map { thread ->
    thread.copy(
        messages = thread.messages.filter {
            it.text == "@"
        }
    )
}

Edit (solution if your classes are mutable)

If your classes are mutable then it's similar but a bit different:

threadList.forEach { thread ->
    thread.removeIf { message ->
      message.text != "@"
    }
}

edited Feb 11, 2021 at 10:19

answered Feb 11, 2021 at 8:22

Tarmo

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