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What's the Kotlin generic type to capture a MutableMap and a MutableList?


What's the Kotlin generic type to capture a MutableMap and a MutableList?

By : Gnob
Date : October 17 2020, 06:10 AM
With these it helps Why don't you just use the field size found both on Collection and Map?
code :
public interface Collection<out E> : Iterable<E> {
    // Query Operations
    /**
     * Returns the size of the collection.
     */
    public val size: Int

    ...
}
public interface Map<K, out V> {
    // Query Operations
    /**
     * Returns the number of key/value pairs in the map.
     */
    public val size: Int

    ...
}


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How do I initialize Kotlin's MutableList to empty MutableList?

How do I initialize Kotlin's MutableList to empty MutableList?


By : G. Botha
Date : March 29 2020, 07:55 AM
like below fixes the issue Seems so simple, but, how do I initialize Kotlin's MutableList to empty MutableList? , You can simply write:
code :
val mutableList = mutableListOf<Kolory>()
val mutableList : MutableList<Kolory> = arrayListOf()
val mutableList : MutableList<Kolory> = ArrayList()
Kotlin mutableMap.put returns nullable

Kotlin mutableMap.put returns nullable


By : Ward Greunke
Date : March 29 2020, 07:55 AM
it helps some times In kotlin standard lib we have MutableMap interface which has this method , Take a look at the definition
code :
/**
 * Associates the specified [value] with the specified [key] in the map.
 *
 * @return the previous value associated with the key, or `null` if the key was not present in the map.
 */
public fun put(key: K, value: V): V?
fun main(args: Array<String>) {
    var m: MutableMap<Int, String> = mutableMapOf(Pair(1, "a"))
    val prev1Value = m.put(1, "b")
    val prev2Value = m.put(2, "c")

    println(m)
    println("Previous value of 1 was: $prev1Value")
    println("Previous value of 2 was: $prev2Value")
}
{1=b, 2=c}
Previous value of 1 was: a
Previous value of 2 was: null
What's the difference between HashMap and MutableMap in Kotlin

What's the difference between HashMap and MutableMap in Kotlin


By : Tiffany Thomas
Date : March 29 2020, 07:55 AM
will help you HashMap is an implementation of the interface MutableMap. From the former link:
Kotlin mutableMap automatically changing in android?

Kotlin mutableMap automatically changing in android?


By : user3642113
Date : March 29 2020, 07:55 AM
I hope this helps . Not sure how you assign _mapData from mapData, but if you simply write:
code :
_mapData = viewModel.mapData
_mapData = viewModel.mapData.toMutableMap()
Kotlin mutableMap foreach

Kotlin mutableMap foreach


By : İlhami Alkan
Date : March 29 2020, 07:55 AM
seems to work fine The lambda that you pass to forEach { ... } accepts an Entry, and you can work with this entry, accessing its value:
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