Importing the package

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.block.IBlockDefinition;

Calling an IBlockDefinition object

Using the definition ZenGetter on an IBlock object.

Calling an IBlockDefinition List

Using game.blocks to get a list of all block definition in the game.

ZenGetters/ZenSetters

ZenGetter	ZenSetter	What does it do	Type
ZenGetter canSpawnInBlock	ZenSetter	What does it do Returns true if an entity can spawn in this block	Type bool
ZenGetter creativeTab	ZenSetter creativeTab	What does it do	Type ICreativeTab
ZenGetter defaultState	ZenSetter	What does it do	Type IBlockState
ZenGetter	ZenSetter defaultSlipperiness	What does it do	Type float
ZenGetter id	ZenSetter	What does it do Returns the block ID	Type string
ZenGetter displayName	ZenSetter	What does it do Returns the block’s DisplayName	Type string
ZenGetter hardness	ZenSetter hardness	What does it do	Type int
ZenGetter harvestLevel	ZenSetter	What does it do Returns the block’s harvest level	Type int
ZenGetter harvestTool	ZenSetter	What does it do Returns the block’s harvest tool	Type string
ZenGetter lightOpacity	ZenSetter lightOpacity	What does it do	Type int
ZenGetter lightLevel	ZenSetter lightLevel	What does it do	Type int
ZenGetter resistance	ZenSetter resistance	What does it do	Type int
ZenGetter unlocalizedName	ZenSetter	What does it do Returns the block’s unlocalized Name	Type string
ZenGetter tickRandomly	ZenSetter tickRandomly	What does it do	Type bool

ZenMethods

Set Block unbreakable

Uses no paramaeters.
Returns nothing.
Does the same as hardness = -1;

defObj.setUnbreakable();

Get tickrate in a specific world

Uses an IWorld object.
Returns an int.

defObj.getTickRate(IWorld world);

Check if the block can be placed on another block

Uses an IWorld object, an IBlockPos object and, depending on the method used, also an IFacing object.
Returns a bool.

defObj.canPlaceBlockOnSide(IWorld world, IBlockPos pos, IFacing facing);
defObj.canPlaceBlockAt(IWorld world, IBlockPos pos);

Get the block’s slipperiness

Uses an IBlockState, an IBlockAccess object, an IBlockPos and an optional IEntity object.
Returns a float.

defObj.getSlipperiness(IBlockState state, IBlockAccess access, IBlockPos pos, @Optional IEntity entity);

Set the block’s harvest level

Uses a string, an int and an optional IBlockState.
if the IBlockState argument is ignored, it will set harvest level to all block states in the block definition.
Returns void (nothing).

defObj.setHarvestLevel(string toolclass, int level, @Optional IBlockState state);

Get harvest level of block state

returns an int.

defObj.getHarvestLevel(IBlockState state);

Get harvest tool of block state

returns a string.

defObj.getHarvestTool(IBlockState state);

Get light opacity of block state

returns a float.

defObj.getLightOpacity(IBlockState state);
defObj.getLightOpacity(IBlockState state, IWorld world, IBlockPos pos);

Get light level of block state

returns a float.

defObj.getLightLevel(IBlockState state);
defObj.getLightLevel(IBlockState state, IWorld world, IBlockPos pos);

Get explosion resistance of block position and explosion

returns a float.

defObj.getResistance(IWorld world, IBlockPos pos, IEntity entity, IExplosion explosion);

Get a block state by metadata

Uses an int.
Returns an IBlockState.

defObj.getStateFromMeta(int meta);

Block effective for the tool

Uses a string and an IBlockState.
Returns a bool.

defObj.isToolEffective(String type, IBlockState state);