I have tried to loop through the properties of the blockstate and get their values so i can set them in another blockstate

Collection<Property<?>> properties = blockstate1.getProperties();

for (Property<?> property : properties) {
                    if (blockstate2.hasProperty(property)) {
                        blockstate2 = blockstate2.setValue(property, blockstate1.getValue(property));
                    }
                }

However, that gives me this error in the setValue method:

Incompatible equality constraint: capture of ? and capture of ?

I know that it has probably something to do with the type parameters in the setValue method but what confuses me is that it works for the hasProperty and the getValue method

Java questions are not answered here.

 

Explain why you need to do this?

BlockStates with the same property values should be the same Object instance.

 

BlockState.setValue() does not create a new BlockState instance.

It selects an already existing BlockState from the set of possible states using the reference BlockState and the new property value.

 

The possible BlockStates are created by the Block's createBlockStateDefinition()

 

e.g. from BambooBlock

This creates 2 (age) * 3 (leaves) * 2 (stage) = 12 BlockStates

   protected void createBlockStateDefinition(StateDefinition.Builder<Block, BlockState> p_48928_) {
      p_48928_.add(AGE, LEAVES, STAGE);
   }

while this selects one of them as the default state

      this.registerDefaultState(this.stateDefinition.any().setValue(AGE, Integer.valueOf(0)).setValue(LEAVES, BambooLeaves.NONE).setValue(STAGE, Integer.valueOf(0)));

 

Edited September 23, 20223 yr by warjort

What I wanted to do was to just change a block to a different block but I wanted some values to be the same so that if I for example changed oak stairs into birch stairs that it would keep the rotation etc.

Then you need to tell the compiler what you are doing.

You are currently effectively trying to use setValue(Property<?>, ?) and the compiler has no way of knowing if those two ?s have the same type.

? means they could have any type/value. Hence your compiler error.

e.g. try something like this (untested code)

        BlockState oak = Blocks.OAK_STAIRS.getStateDefinition().any();
        BlockState acacia = Blocks.ACACIA_STAIRS.defaultBlockState();
        for (Property<?> property : oak.getProperties()) {
            acacia = copyProperty(oak, acacia, property);
        }

        // You are telling the compiler the two parameters use the same T
        private static <T extends Comparable<T>> BlockState copyProperty(BlockState from, BlockState to, Property<T> property) {
            return to.setValue(property, from.getValue(property));
        }

 

Edited September 23, 20223 yr by warjort

Thank you very much
Works like a charm