I've been looking through vanilla and I think this works.  Would someone confirm if I've got this right or if I'm missing stuff.

 

My goal is to put down a custom bed in place of the normal one so it doesn't blow up in my custom dimensions.

 

 

 

 

                    // Get current meta

                    IBlockState state = world.getBlockState(pos_Temp);

                   

                    // Change the block with the meta intact

                        world.getBlockState(pos_Temp).withProperty(BlockBed.PART, state.getValue(BlockBed.PART)).withProperty(BlockDirectional.FACING, state.getValue(BlockDirectional.FACING));

                   

 

 

 

Looking at the bed in 1.8, I see another way around this in terms of avoiding the explosion.

 

However, I still would like to know about the state copy I put above.

I think you should use World#setBlockState(...)

Just noticed some of my code was wrapped weird in the post.  might be hard to read.

 

If I setBlockState, that sets the entire block again.  I just want to modify a few of the state properties and leave the rest alone.

Then there is no way theoretically...

IBlockState

s are immutable.

IBlockState#withProperty

returns a different

IBlockState

instance with the property set to the specified value rather than modifying the existing instance.

 

If you want to change the state of a block in the world, you have to use

World#setBlockState

. Simply calling

IBlockState#withProperty

and not doing anything with the result does nothing.

 

Your code will correctly preserve any properties except the ones you change, though.

I get it now.  Thank you Choonster.