Referenced by http://stackoverflow.com/q/37593738/986533

use_case_for_init_delegate_in_ctor.kt

// I want to do the following:
val myTable1 = MyTable() 
// where MyTable inherits from ImmutableTable [1], or at least Table [2], and I do not have to manually delegate all the Table methods to some base implementation.
// I also want to avoid the following:
val myTable2 = MyTable.build() 
// i.e. I do not want to be forced to use companion objects / static factory methods. 

// Reference:
// [1] ImmutableTable source: http://google.github.io/guava/releases/snapshot/api/docs/src-html/com/google/common/collect/ImmutableTable.html#line.45
// [2] Guava immutable collections: https://github.com/google/guava/wiki/NewCollectionTypesExplained#table

// Here is what I tried:

class MyTable_Attempt1 : ImmutableTable<Int, Int, Int> // ERROR: This type has a constructor, and thus must be initialized here
{
  override fun rowMap(): ImmutableMap<Int, MutableMap<Int, Int>>? {
    throw UnsupportedOperationException()
  }

  override fun columnMap(): ImmutableMap<Int, MutableMap<Int, Int>>? {
    throw UnsupportedOperationException()
  }

  override fun size(): Int {
    throw UnsupportedOperationException()
  }
}

class MyTable_Attempt2(val table: ImmutableTable<Int, Int, Int>): Table<Int, Int, Int> by table
{
  // Note: I cannot delegate to ImmutableTable, getting ERROR: Only interfaces can be delegated to
  
  init {
    table = ImmutableTable.of() // ERROR: Val cannot be reassigned
  }
}

class MyTable_Attempt3(var table: ImmutableTable<Int, Int, Int> ): Table<Int, Int, Int> by table
{
  // Note: I cannot delegate to ImmutableTable, getting ERROR: Only interfaces can be delegated to

  init {
    table = ImmutableTable.of()
    // Well OK, it works, but then table can be reassigned later on, as it is "var" not "val" :(
  }
}