Accessor<T extends Component> extension type

One entity seen as its T component - what entity<Transform3D>() returns, and where a component's helper methods live.

A helper reached this way takes only what it is about, because the entity it operates on is the receiver:

entity<Transform3D>().setEuler(yaw: 0.5);
entity<Transform3D>().lookAt(0, 0, 0);
final gap = entity<Transform3D>().distanceTo(other);

Writing one for your own component

Declare an extension named after the component, on Accessor of it:

mixin Health on Component {
  late final DataPointer<int> hp;

  @override
  void describeStruct(DataDescriptor data) {
    super.describeStruct(data);
    hp = data.hasInt32(100);
  }
}

extension HealthAccessor on Accessor<Health> {
  void damage(int amount) {
    final health = component;
    health.hp[this] = health.hp[this] - amount;
  }
}

Inside the extension this is the entity, so a column indexes with this directly, and component hands back the Health it belongs to. Hold that in a local when you touch it more than once - each read resolves the component again.

A helper taking a second entity reads that one through its own component (other.get<Health>()), because it may be a different archetype with a different row layout. Only the receiver is guaranteed to be this one.

Everything on Entity is available too - destroy(), sceneSlot, tryGet - and an accessor can be passed anywhere an entity is wanted, because it implements Entity.

Why the helpers go here and not on the component

Two components can want the same method name, and Accessor<Health> and Accessor<Transform3D> are different types, so each can declare distanceTo or damage without the two colliding in a library that imports both. A helper put on the component mixin, or on Entity itself, has no such separation.

It costs nothing: Accessor<T> erases to Entity, which erases to int, so identical(entity<T>().entity, entity) holds and nothing is allocated to reach a helper.

on

Entity

Implemented types

Entity

Available extensions

Constructors

Accessor(Entity entity): const

Properties

address → Pointer<Never>: Available on int, provided by the IntAddress extension
The memory address of the underlying data.
no setter
archetypeId → int: no setterinherited
bitLength → int: Returns the minimum number of bits required to store this integer.
no setterinherited
component → T: no setter
entity → Entity: final
hashCode → int: Returns a hash code for a numerical value.
no setterinherited
isEven → bool: Returns true if and only if this integer is even.
no setterinherited
isFinite → bool: Whether this number is finite.
no setterinherited
isInfinite → bool: Whether this number is positive infinity or negative infinity.
no setterinherited
isNaN → bool: Whether this number is a Not-a-Number value.
no setterinherited
isNegative → bool: Whether this number is negative.
no setterinherited
isOdd → bool: Returns true if and only if this integer is odd.
no setterinherited
oneBitCount → int: The number of 1 bits in the binary representation of this integer.
no setterinherited
pageIndex → int: no setterinherited
rowOffset → int: no setterinherited
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
scene → Scene: Available on Entity, provided by the EntityLifetime extension
The loaded scene this entity lives in.
no setter
sceneSlot → int: Which loaded scene this row belongs to, as Scene.slot, or -1 if its page has been freed or it was created outside any scene.
no setterinherited
sign → int: Returns the sign of this integer.
no setterinherited
toJS → JSNumber: Available on num, provided by the NumToJSExtension extension
Converts this num to a JSNumber.
no setter
trailingZeroBitCount → int: The number of trailing (least significant) zero bits in the binary representation of this integer.
no setterinherited
value → int: finalinherited

Methods

abs() → int: Returns the absolute value of this integer.
inherited
addChild(Entity child) → void: Available on Accessor<Parent>, provided by the ParentAccessor extension
Appends child to the end of this entity's child list - a doubly-linked splice through firstChild/lastChild and child's own nextSibling/prevSibling.
adopt(Entity child) → void: Available on Accessor<Parent>, provided by the ParentAccessor extension
Moves child here from wherever it is, keeping it and its subtree alive
call<T extends Component>() → Accessor<T>: This entity, seen as its T component:
inherited
ceil() → int: Returns this.
inherited
ceilToDouble() → double: Returns this.toDouble().
inherited
clamp(num lowerLimit, num upperLimit) → num: Returns this num clamped to be in the range lowerLimit-upperLimit.
inherited
compareTo(num other) → int: Compares this to other.
inherited
destroy() → void: Available on Entity, provided by the EntityLifetime extension
Destroys one entity: its subtree, then its links, then its row.
detach() → void: Available on Accessor<Child>, provided by the ChildAccessor extension
Unlinks this entity from its parent, keeping it and its subtree alive.
floor() → int: Returns this.
inherited
floorToDouble() → double: Returns this.toDouble().
inherited
gcd(int other) → int: Returns the greatest common divisor of this integer and other.
inherited
get<T extends Component>() → T: The prefab describing this entity's archetype - the instance holding the DataPointer fields the struct's mixins wrote into their late finals. Combine with the entity itself to reach data: instance.get<Transform2D>().transformOffsetX[instance].
inherited
modInverse(int modulus) → int: Returns the modular multiplicative inverse of this integer modulo modulus.
inherited
modPow(int exponent, int modulus) → int: Returns this integer to the power of exponent modulo modulus.
inherited
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
remainder(num other) → num: The remainder of the truncating division of this by other.
inherited
removeChild(Entity child) → void: Available on Accessor<Parent>, provided by the ParentAccessor extension
Destroys child and everything under it.
round() → int: Returns this.
inherited
roundToDouble() → double: Returns this.toDouble().
inherited
toDouble() → double: This number as a double.
inherited
toInt() → int: Truncates this num to an integer and returns the result as an int.
inherited
toRadixString(int radix) → String: Converts this int to a string representation in the given radix.
inherited
toSigned(int width) → int: Returns the least significant width bits of this integer, extending the highest retained bit to the sign. This is the same as truncating the value to fit in width bits using an signed 2-s complement representation. The returned value has the same bit value in all positions higher than width.
inherited
toString() → String: Returns a string representation of this integer.
inherited
toStringAsExponential([int? fractionDigits]) → String: An exponential string-representation of this number.
inherited
toStringAsFixed(int fractionDigits) → String: A decimal-point string-representation of this number.
inherited
toStringAsPrecision(int precision) → String: A string representation with precision significant digits.
inherited
toUnsigned(int width) → int: Returns the least significant width bits of this integer as a non-negative number (i.e. unsigned representation). The returned value has zeros in all bit positions higher than width.
inherited
truncate() → int: Returns this.
inherited
truncateToDouble() → double: Returns this.toDouble().
inherited
tryGet<T extends Component>() → T?: get, but null instead of throwing when the archetype lacks T - the OptWith<Child>() half of a query.
inherited

Operators

operator %(num other) → num: Euclidean modulo of this number by other.
inherited
operator &(int other) → int: Bit-wise and operator.
inherited
operator *(num other) → num: Multiplies this number by other.
inherited
operator +(num other) → num: Adds other to this number.
inherited
operator -(num other) → num: Subtracts other from this number.
inherited
operator /(num other) → double: Divides this number by other.
inherited
operator <(num other) → bool: Whether this number is numerically smaller than other.
inherited
operator <<(int shiftAmount) → int: Shift the bits of this integer to the left by shiftAmount.
inherited
operator <=(num other) → bool: Whether this number is numerically smaller than or equal to other.
inherited
operator ==(Object other) → bool: Test whether this value is numerically equal to other.
inherited
operator >(num other) → bool: Whether this number is numerically greater than other.
inherited
operator >=(num other) → bool: Whether this number is numerically greater than or equal to other.
inherited
operator >>(int shiftAmount) → int: Shift the bits of this integer to the right by shiftAmount.
inherited
operator >>>(int shiftAmount) → int: Bitwise unsigned right shift by shiftAmount bits.
inherited
operator [](Child child) → Entity: Available on Accessor<Parent>, provided by the ParentAccessor extension
The entity of child that this one owns - the other half of what EntityStruct.of declares.
operator ^(int other) → int: Bit-wise exclusive-or operator.
inherited
operator unary-() → int: Return the negative value of this integer.
inherited
operator |(int other) → int: Bit-wise or operator.
inherited
operator ~() → int: The bit-wise negate operator.
inherited
operator ~/(num other) → int: Truncating division operator.
inherited