DynamicSupervisor
DynamicSupervisor — Abstract base class for dynamic OTP supervision trees.
Subclass DynamicSupervisor to define a dynamic supervision tree: one
where children are added at runtime rather than declared at startup.
Override class childClass to declare which actor class this pool manages.
See ADR 0059 for the full design.
Examples
DynamicSupervisor(Worker) subclass: WorkerPool
class childClass => Worker
pool := (WorkerPool supervise) unwrap
w := pool startChild unwrap // => Worker (type-narrowed via C)
pool count // => 1
@see Supervisor (for static children declared at startup) @see Actor (base class for supervised processes)
Methods
Class Methods
Maximum number of restarts within restartWindow seconds.
If this rate is exceeded, the supervisor itself shuts down.
Time window in seconds for the maxRestarts rate limit.
Whether this class is a supervisor (always true for DynamicSupervisor subclasses).
Used by SupervisionSpec childSpec to determine type and shutdown.
Return the actor class that this dynamic supervisor manages.
Must be overridden by concrete subclasses. Raises SubclassResponsibility otherwise.
Examples
DynamicSupervisor(Worker) subclass: WorkerPool
class childClass => Worker
Lifecycle hook called after the dynamic supervisor has started.
Override to perform post-start setup (e.g., pre-populating workers
via startChild). Runs in the caller's process, so supervisor
calls will not deadlock.
Examples
DynamicSupervisor(Worker) subclass: WorkerPool
class childClass => Worker
class initialize: sup =>
3 timesRepeat: [sup startChild unwrap]
Start this dynamic supervisor (or return the already-running instance).
ADR 0080 Phase 2 (BT-1999): returns Result(Self, Error). Use
unwrap for boot-style "crash on failure" call sites, or
ifOk:ifError: / andThen: for recoverable starts. Failures surface
as Result error: #beamtalk_error{kind = supervisor_start_failed}.
Return the running supervisor instance, or nil if not started.
Instance Methods
Start a new child with default args.
ADR 0080 Phase 2 (BT-1999): returns Result(C, Error). Use unwrap
when failure should propagate as an exception, or ifOk:ifError: /
andThen: for recoverable starts. Failures surface as
Result error: #beamtalk_error{kind = child_start_failed}.
Start a new child with the given initialization args.
ADR 0080 Phase 2 (BT-1999): returns Result(C, Error). Use unwrap
when failure should propagate as an exception, or ifOk:ifError: /
andThen: for recoverable starts. Failures surface as
Result error: #beamtalk_error{kind = child_start_failed}.
Terminate the given child process.
ADR 0080 Phase 2 (BT-1999): returns Result(Nil, Error). Idempotent
on not_found — terminating an already-gone child returns
Result ok: nil. Genuine failures surface as
Result error: #beamtalk_error{kind = terminate_failed}.
Return the count of currently-running children.
BT-1997 / ADR 0080 Phase 1: countChildren/1 returns a Result-shaped
value; call unwrap at the FFI boundary to preserve the pre-migration
user-facing signature.
Internal FFI seam (ADR 0101 Part 4): the raw Result-shaped
countChildren/1 call. Keeps count pure Beamtalk.
Stop this supervisor and all its children.
BT-1997 / ADR 0080 Phase 1: stop/1 returns a Result-shaped value;
call unwrap at the FFI boundary to preserve the pre-migration
user-facing signature.
Internal FFI seam (ADR 0101 Part 4): the raw Result-shaped stop/1
call. Keeps stop pure Beamtalk.
Inherited Methods
From Object
Return the class of the receiver.
Examples
42 class // => Integer
"hello" class // => String
Test if the receiver is nil. Returns false for all objects except nil.
Examples
42 isNil // => false
nil isNil // => true
Test if the receiver is not nil. Returns true for all objects except nil.
Examples
42 notNil // => true
nil notNil // => false
If the receiver is nil, evaluate nilBlock. Otherwise return self.
Examples
42 ifNil: [0] // => 42
nil ifNil: [0] // => 0
If the receiver is not nil, evaluate notNilBlock with self.
Examples
42 ifNotNil: [:v | v + 1] // => 43
nil ifNotNil: [:v | v + 1] // => nil
If nil, evaluate nilBlock; otherwise evaluate notNilBlock with self.
Examples
42 ifNil: [0] ifNotNil: [:v | v + 1] // => 43
nil ifNil: [0] ifNotNil: [:v | v + 1] // => 0
If not nil, evaluate notNilBlock with self; otherwise evaluate nilBlock.
Examples
42 ifNotNil: [:v | v + 1] ifNil: [0] // => 43
nil ifNotNil: [:v | v + 1] ifNil: [0] // => 0
Return the developer-readable (Debug) string representation.
printString is the Debug protocol (ADR 0094): the self-describing,
structural form used by the REPL, logs, and by any other printString
that nests this object. It is the REPL default — evaluating an expression
shows its printString.
This default returns the bare class name (no a/an article — the
old "a ClassName" form was dropped in ADR 0094). Value overrides it
with the structural ClassName(field: value, ...) form, actors render as
Actor(ClassName, pid), supervisors as Supervisor(ClassName, pid) /
DynamicSupervisor(ClassName, pid), and primitive types (Integer, String,
List, …) override it with their own richer output. Authors rarely override
printString directly — the default is derived.
Examples
42 printString // => "42"
Return the user-facing (Display) string representation.
displayString is the Display protocol (ADR 0094): the human-facing
form. It is the hook the language pulls during string interpolation —
every {...} segment renders via the value's displayString. Developers
rarely call it directly; they override it when a value has a natural
human rendering (e.g. Money → $10.50, where printString would still
show the Debug form).
It defaults to printString, so most types need no override. String
and Symbol demonstrate the split: "hi" printString → "\"hi\""
(quoted, Debug) while "hi" displayString → "hi" (plain, Display);
likewise #foo drops its # prefix under displayString.
displayString is not part of the Printable protocol (deferred per
ADR 0094 §5).
Examples
42 displayString // => "42"
Open a navigable Inspector cursor on the receiver.
ADR 0095 Phase 3 (BT-2504). inspect is repurposed from -> String
(the ADR-0094 deferral) to the verb that produces an Inspector — a
live, immutable cursor for drilling into the object (Inspector on: self).
anObject inspect is the shorthand; Inspector on: anObject is the
explicit spelling. The cursor exposes fields/at:/path/refresh/
printString (an indented text tree) and asDictionaries (the MCP/browser
wire form); see Inspector.
This is a breaking change: code that used inspect for its old
String result must switch to printString (the structural Debug string,
ADR 0094) — a transitional lint flags inspect used directly in ++/
string position.
Examples
42 inspect kind // => #value
(Point x: 3 y: 4) inspect fields size // => 2
(Point x: 3 y: 4) printString // => "Point(x: 3, y: 4)" (the old inspect string)
Return the receiver itself. Useful for cascading side effects.
Examples
42 yourself // => 42
Return a hash value for the receiver.
Examples
42 hash
Test if the receiver responds to the given selector.
Examples
42 respondsTo: #abs // => true
Return the names of fields.
Examples
42 fieldNames // => #()
Return the value of the named field.
Examples
object fieldAt: #name
Set the value of the named field (returns new state).
Examples
object fieldAt: #name put: "Alice"
Send a unary message dynamically.
Examples
42 perform: #abs // => 42
Send a message dynamically with arguments.
Examples
3 perform: #max: withArguments: #(5) // => 5
Raise an error indicating this method must be overridden by a subclass.
Examples
self subclassResponsibility
Raise an error indicating this method has not yet been implemented.
Use this for work-in-progress stubs. Distinct from subclassResponsibility,
which signals an interface contract violation.
Examples
self notImplemented
Send aValue to the current transcript without a trailing newline.
Nil-safe: does nothing when no transcript is set (batch compile, tests).
Examples
42 show: "value: "
Send aValue to the current transcript followed by a newline.
Nil-safe: does nothing when no transcript is set (batch compile, tests).
Examples
42 showCr: "hello world"
Test if the receiver is an instance of aClass or any of its subclasses.
For class-object receivers, follows Smalltalk semantics: self class
is the metaclass, so the check walks the parallel metaclass hierarchy.
The parallel chain is grounded at ProtoObject class superclass == Class
(ADR 0036), so the metaclass tower merges into the instance-side
Class → Behaviour → Object → ProtoObject chain. As a result,
Integer isKindOf: Object and Integer isKindOf: Class both return true.
Examples
42 isKindOf: Integer // => true
42 isKindOf: Object // => true
#foo isKindOf: Symbol // => true
#foo isKindOf: String // => false
Integer isKindOf: Number // => false (metaclass chain, not instance chain)
Integer isKindOf: Number class // => true (Number class is in the parallel chain)
Integer isKindOf: Object // => true (grounded — Object is reachable via the metaclass tower)
Integer isKindOf: Class // => true (Integer class inherits from Class)
Raise an error with the given message.
Examples
self error: "something went wrong"
Delegate message dispatch to the backing Erlang module (ADR 0101, BT-2720).
This method is a sentinel — a plain Object has no backing Erlang module,
so calling delegate raises an Error at runtime. Stateless Objects
declared with native: have their self delegate method bodies rewritten
by the compiler's codegen phase to call the backing module directly, so the
sentinel is never reached on a native: class.
Unlike Actor's delegate (visible only to Actor subclasses), this
Object-base sentinel is visible to every class, so delegate is a
reserved selector on the Object protocol.
Examples
42 delegate // => ERROR: delegate called on a non-native Object
From ProtoObject
Test value equality (Erlang ==).
Examples
42 == 42 // => true
"abc" == "abc" // => true
Test value inequality (negation of ==).
Examples
1 /= 2 // => true
42 /= 42 // => false
Return the class of the receiver.
Examples
42 class // => Integer
"hello" class // => String
Handle messages the receiver does not understand. Override for custom dispatch.
Examples
42 unknownMessage // => ERROR: does_not_understand
Send a message dynamically with an arguments list.
Examples
42 perform: #abs withArguments: #() // => 42
Execute a class method in the caller's process, bypassing gen_server dispatch.
The caller takes responsibility for knowing the method does not mutate class state. Useful for long-running class methods that would otherwise block the class object's gen_server.
Limitations: only resolves methods defined directly on the target class
module (does not walk the superclass chain). Class variables and self
are not available to the method (nil and #{} are passed).
Examples
MyClass performLocally: #run:ctx: withArguments: #(input, ctx)
Send a message dynamically with an arguments list and explicit timeout.
The timeout (in milliseconds or #infinity) applies to the gen_server:call
when the receiver is an actor. For value types, timeout is ignored.
Examples
actor perform: #query withArguments: #(sql) timeout: 30000