here i tried to reproduce my problem .. for set ...

# getting-started

[abu naser]

here i tried to reproduce my problem .. for set of custom data filter and then remove is not working but remove if is working fine.. and if any inner value not change then its works ..

import org.junit.Test

class TestMutableSetDelete {
    @Test
    fun testRemoveMutableSet(){
        val data = TestSetList(mutableSetOf(), mutableSetOf())
        add(data)
        change(data)
        //deletes not work in any inner value ever change 
        delete(data)
        // removeIf always works . but i my code need to work below api 24 too.
//        data.span.removeIf { it.start==it.end }
        // FIXME: without change this works . but if change happend its not
        data.range.forEach { println("start > ${it.start} > ${it.end}") }
        assert(data.range.size==2)
    }
}
data class TestSetList(
    val range: MutableSet<Range> = mutableSetOf(),
    val para: MutableSet<Para> = mutableSetOf()
)
data class Para(
    val start:Int,
    val end:Int
)
data class ChangedData(
    var name:String="",
    var age:Long
)
data class Range(
    val start:Int,
    val end:Int,
    val changedData: ChangedData
)
fun add(data:TestSetList){
    val cd =ChangedData("naser",26)
    data.range.add(Range(0,0,cd))
    data.range.add(Range(1,2,cd))
    data.range.add(Range(1,5,cd))
    data.range.add(Range(2,2,cd))
    data.range.add(Range(3,3,cd))
}
fun change(data: TestSetList){
    //simulate some change in the process .
    data.range.forEach { it.changedData.name = it.start.toString() }
}
fun delete(data:TestSetList){
    data.range.filter { it.start == it.end }.forEach { data.range.remove(it) }
}

[Ioannis Mavroukakis]

I ran your test as-is, and it did not fail 😕

[Ioannis Mavroukakis]

ah wait, assertions not on.

[abu naser]

check this .. the value that are equal ( start == end ) is still there ..

[abu naser]

this one with remove if

[abu naser]

this time out of function ,, and tried both filter and if .. not works either .. why though ?

[Michael de Kaste]

I don't know exactly whats happening underwater, maybe someone else can give some light on that but:

You shouldn't ever alter the way a class maps its equality AFTER insertion into a set, since equality is checked at insertion-time.

Consider this: You have a class with a single var, you insert 5 different values of this class; afterwards, you assign all these vars the same value. The result is a set of 5 elements whom are all equal. Which is counterproductive to what you initially wanted.

[Michael de Kaste]

from the docs from java itself:

Note: Great care must be exercised if mutable objects are used as set elements. The behavior of a set is not specified if the value of an object is changed in a manner that affects equals comparisons while the object is an element in the set. A special case of this prohibition is that it is not permissible for a set to contain itself as an element.

[Michael de Kaste]

There are multiple possible variants to work with instead; I'd consider using a Map instead like so:

class TestMutableSetDelete {
    fun testRemoveMutableSet() {
        val data = TestSetList(mutableMapOf(), mutableSetOf())
        add(data)
        change(data)
        delete(data)
        data.range.forEach { println("start > ${it.key.start} > ${it.key.end}") }
        assert(data.range.size == 2)
    }
}
data class TestSetList(
    val range: MutableMap<RangeKey, ChangedData> = mutableMapOf(),
    val para: MutableSet<Para> = mutableSetOf()
)
data class Para(
    val start: Int,
    val end: Int
)
data class ChangedData(
    var name: String = "",
    var age: Long
)
data class RangeKey(
    val start: Int,
    val end: Int
)
fun add(data: TestSetList) {
    val cd = ChangedData("naser", 26)
    data.range[RangeKey(0, 0)] = cd
    data.range[RangeKey(1, 2)] = cd
    data.range[RangeKey(1, 5)] = cd
    data.range[RangeKey(2, 2)] = cd
    data.range[RangeKey(3, 3)] = cd
}
fun change(data: TestSetList) {
    // simulate some change in the process .
    data.range.forEach { (k,v) -> v.name = k.start.toString() }
}
fun delete(data: TestSetList) {
    data.range.keys.filter { it.start == it.end }.forEach { data.range.remove(it) }
}

[Ioannis Mavroukakis]

@Michael de Kaste is spot on, your change messes up the Set equality. Behind the scenes, Set is expressed as keys in a Map

public boolean remove(Object o) {
        return map.remove(o)==PRESENT;
}

[Michael de Kaste]

on last addendum:

fun add(data: TestSetList) {
    val cd = ChangedData("naser", 26)
    data.range[RangeKey(0, 0)] = cd.copy()
    data.range[RangeKey(1, 2)] = cd.copy()
    data.range[RangeKey(1, 5)] = cd.copy()
    data.range[RangeKey(2, 2)] = cd.copy()
    data.range[RangeKey(3, 3)] = cd.copy()
}

consider using different actual classes as a value for your keys, otherwise the 5 keys will all point to the same value at which point

fun change(data: TestSetList) {
    // simulate some change in the process .
    data.range.forEach { (k,v) -> v.name = k.start.toString() }
}

does nothing but changes the name of the value on all keys to "3"

[abu naser]

thanks a lot..