AnnouncementNavigation
AnnouncementNavigation — live subscription-graph introspection queries (ADR 0093 §7).
The third navigation sibling, alongside SystemNavigation (static class
registry) and ProcessNavigation (live supervision tree). Where those answer
"who implements #asString" and "what is running, under whose supervision",
AnnouncementNavigation answers "who listens for which events, on which
bus" over the live announcements substrate.
Like its siblings it is a query handle — a sealed typed Object subclass,
not an actor — so its queries run as plain Erlang in the calling eval worker
off direct, concurrent ETS reads (never routed through a gen_server that the
walk could deadlock against). Each query returns a fresh read-only
snapshot of immutable SubscriptionNode value records; to act on a
subscription you cross back to the live Subscription token or Announcer
(the read-vs-mutate rule, ADR 0092 §3a).
Scopes:
AnnouncementNavigation default— the singleton system bus (SystemAnnouncer current).AnnouncementNavigation of: anAnnouncer— a specific announcer.
Each Announcer is isolated (BT-2454), so the two scopes report different
subscription sets: default sees only the system bus, of: anAnnouncer sees
only that announcer's subscriptions. The handle carries the announcer it
navigates (minted via FFI, like Announcer carries its ref), and each
returned SubscriptionNode is stamped with that announcer.
Examples
AnnouncementNavigation default subscriptions
AnnouncementNavigation default subscribersOf: ActorSpawned
AnnouncementNavigation default announcedClasses
(AnnouncementNavigation of: a) subscribersOf: PriceChanged
Methods
Class Methods
A navigation over the singleton system bus (SystemAnnouncer current) —
the default scope, the one feed for everything the system emits.
Examples
AnnouncementNavigation default subscriptions
A navigation over a specific anAnnouncer — reports only that announcer's
subscriptions (BT-2454).
Examples
AnnouncementNavigation of: (Announcer new)
Instance Methods
A read-only snapshot of every live subscription on the navigated announcer,
as immutable SubscriptionNode records. Re-call to refresh.
Examples
AnnouncementNavigation default subscriptions // => [a SubscriptionNode, ...]
A read-only snapshot of the subscriptions to exactly aClass, as
SubscriptionNode records. Matches exactly aClass (not subclasses) — the
as-subscribed key, mirroring when:do:. The IDE's "event wiring" pane
(ADR 0017/0091) groups this by announcementClass.
Examples
AnnouncementNavigation default subscribersOf: ActorSpawned
The distinct event classes currently subscribed to on the navigated announcer — the event types in active use, as class objects (ADR 0093 §7). Classes with live subscriptions appear once each; the order is unspecified.
Examples
AnnouncementNavigation default announcedClasses // => [ActorSpawned, PriceChanged]
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.
_nilBlock is never evaluated on this Object-level definition (only
UndefinedObject's override calls it, with Block(R) -> R), so R is
unconstrained here — parameterizing it still documents the zero-arg
shape without implying this branch produces R (BT-2834).
Examples
42 ifNil: [0] // => 42
nil ifNil: [0] // => 0
If the receiver is not nil, evaluate notNilBlock with self.
Left as a bare Block deliberately (BT-2834): notNilBlock is invoked
one-arg with self and its result becomes the method's own result, so
a precise signature needs a Self-in-Block(...) type-arg form
(Block(Self, R) -> R) with no precedent elsewhere in stdlib. The type
checker doesn't consult this declared signature for ifNotNil: anyway
— it narrows the block's parameter from the receiver's own type via
infer_args_for_if_not_nil in inference.rs (BT-2046), independent of
this stdlib declaration.
Examples
42 ifNotNil: [:v | v + 1] // => 43
nil ifNotNil: [:v | v + 1] // => nil
If nil, evaluate nilBlock; otherwise evaluate notNilBlock with self.
Bare Block params here (unlike UndefinedObject's Block(R) -> R
override, BT-2824) are intentional, not an oversight: the type checker
never consults this declared signature for these two selectors — it
reads the block arguments' actual inferred return types directly
(if_nil_branch_union_ret_ty in inference.rs, BT-2047) since a bare
-> R here can't express "whatever the block returns" without a
Self-in-Block(...) type-arg form with no precedent elsewhere in
stdlib.
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.
See ifNil:ifNotNil: above — the bare Block params are intentional.
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 value equality — the overridable counterpart to =:=.
Defaults to =:= (Erlang structural term equality), so for most classes
the two agree. Unlike =:=, this is an ordinary message send, so a class
whose logical value is not its representation can override it: a
persistent structure whose shape depends on construction history, a
timestamp that should compare by instant rather than by wall-clock fields,
or a type with a normalising form. =:=, =/=, == and /= are lowered
straight to Erlang BIFs (ADR 0002) and cannot be overridden — the compiler
rejects any attempt (BT-2997).
What honours it
The linear scans: includes: on Collection, List, Array and
Dictionary (which searches values), plus List>>indexOf: and
TestCase>>assert:equals:.
Contract
An override must agree with =:= wherever =:= holds — a =:= b must
imply a equals: b. It may only make more values equal, never fewer.
The scans above rely on this: each tries raw =:= first and dispatches
only on a miss, so a fast-path hit is always a genuine equals: hit.
Caveat
Set, Dictionary keys, and List>>unique decide identity in the VM
with raw =:=, never through this method — keying and deduplication need
an order or a hash that a user-defined equals: cannot supply. A class
that overrides equals: still deduplicates by representation when used
as a key or element. Normalise the representation if that matters.
Examples
42 equals: 42 // => true
42 equals: 42.0 // => false (defaults to strict `=:=`)
"ab" equals: "ab" // => true
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 ==, non-strict — 1 == 1.0 is true).
Examples
42 == 42 // => true
"abc" == "abc" // => true
Test value inequality (negation of ==).
Examples
1 /= 2 // => true
42 /= 42 // => false
Test strict value equality (Erlang =:= — 1 =:= 1.0 is false, unlike ==).
Every object supports this at runtime (it lowers directly to Erlang's
=:= operator regardless of receiver type, ADR 0002) — declared here,
once, so it is visible in method listings/completions/respondsTo: for
every class, not just the handful (Integer, String, ...) that
separately redeclare it with a narrower, class-typed other for
documentation purposes.
Examples
1 =:= 1 // => true
1 =:= 1.0 // => false (strict — different types)
(Dictionary new) =:= #{} // => true
Test strict value inequality (negation of =:=).
Examples
1 =/= 1.0 // => true (strict — different types)
1 =/= 1 // => 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