``` class CounterMap(val map: MutableMap<String...

# getting-started

[Andreas Sinz]

class CounterMap(val map: MutableMap<String, Int>): MutableMap<String, Int> by map {
    override fun put(key: String, value: Int): Int? {
        val previousValue = map[key]
        
        map[key] = (previousValue ?: 0 ) + value
        	
        return previousValue
    }
}

[nkiesel]

d3xter: Actually I think I would have to override get:

class CounterMap<K, V>(val map: MutableMap<K, V>, val default: V): MutableMap<K, V> by map {
override fun get(key: K): V {
return map[key] ?: default
}
}

[nkiesel]

also asked in #stdlib , thanks for the tip

[Andreas Sinz]

you are right. its better to override get()