File

Inherits from Object

File — File system operations.

Provides file I/O operations and lazy file streaming using Erlang's file module. All operations are class methods. Errors use structured #beamtalk_error{} records.

Examples

File exists: "test.txt"
File readAll: "test.txt"
File writeAll: "output.txt" contents: "hello"
File readBinary: "image.png"
File writeBinary: "output.bin" contents: data
File appendBinary: "log.bin" contents: data
(File lines: "data.csv") do: [:line | Transcript show: line]
File open: "data.csv" do: [:handle | handle lines take: 10]

@see System (for environment variables and OS information) @see Json (for reading/writing JSON files)

Class Methods

exists: path Sealed source

Test if a file exists at the given path (class method).

Examples

File exists: "test.txt"   // => true or false

readAll: path Sealed source

Read the entire contents of a file as a string (class method).

Returns Result ok: contents on success, or Result error: err on failure.

Examples

File readAll: "test.txt"  // => Result ok: "file contents..."

writeAll: path contents: text Sealed source

Write text to a file, creating or overwriting it (class method).

Returns Result ok: nil on success, or Result error: err on failure.

Examples

File writeAll: "output.txt" contents: "hello"

readBinary: path Sealed source

Read the entire contents of a file as raw binary (class method).

Returns Result ok: binary on success, or Result error: err on failure. Unlike readAll:, this does not assume the contents are a UTF-8 string.

Examples

File readBinary: "image.png"  // => Result ok: <<...>>

writeBinary: path contents: binary Sealed source

Write binary data to a file, creating or overwriting it (class method).

Returns Result ok: nil on success, or Result error: err on failure.

Examples

File writeBinary: "output.bin" contents: data

appendBinary: path contents: binary Sealed source

Append binary data to a file, creating it if needed (class method).

Returns Result ok: nil on success, or Result error: err on failure.

Examples

File appendBinary: "log.bin" contents: data

lines: path Sealed source

Return a lazy Stream of lines from a file (class method).

Opens the file and returns Result ok: stream on success, or Result error: err on failure. The Stream reads one line at a time and closes the handle automatically when exhausted. Constant memory — safe for large files.

Cross-process constraint: file-backed Streams must be consumed by the same process that created them.

Examples

(File lines: "data.csv") unwrap take: 5
(File lines: "log.txt") unwrap select: [:l | l includesSubstring: "ERROR"]

open: path do: block Sealed source

Block-scoped file handle with automatic cleanup (class method).

Opens the file, passes a FileHandle to the block, and ensures the handle is closed when the block exits (normally or via exception). Returns Result ok: blockResult on success, or Result error: err on failure.

The handle responds to lines which returns a Stream of lines. Both the handle and any Streams derived from it must be consumed within the block — they must not escape, as the file descriptor is closed when the block returns.

Examples

(File open: "data.csv" do: [:handle |
  handle lines take: 10
]) unwrap

lastModified: path Sealed source

Get the last modification time of a file (class method).

Returns Result ok: DateTime on success, or Result error: err if the file does not exist.

Examples

File lastModified: "test.txt"  // => Result ok: a DateTime(...)

isDirectory: path Sealed source

Test if a path refers to a directory (class method).

Examples

File isDirectory: "target"   // => true or false

isFile: path Sealed source

Test if a path refers to a regular file (class method).

Examples

File isFile: "test.txt"   // => true or false

mkdir: path Sealed source

Create a directory (class method). Error if the parent does not exist.

Returns Result ok: nil on success, or Result error: err on failure.

Examples

File mkdir: "target/mydir"

mkdirAll: path Sealed source

Create a directory and all missing parent directories (class method).

Returns Result ok: nil on success, or Result error: err on failure.

Examples

File mkdirAll: "target/a/b/c"

listDirectory: path Sealed source

List entries in a directory as a List of Strings (class method).

Returns Result ok: list on success, or Result error: err on failure.

Examples

File listDirectory: "target"

delete: path Sealed source

Delete a file or empty directory (class method).

Returns Result ok: nil on success, or Result error: err on failure.

Examples

File delete: "target/old.txt"

deleteAll: path Sealed source

Recursively delete a directory tree (class method).

Returns Result ok: nil on success, or Result error: err on failure.

Examples

File deleteAll: "target/old-workspace"

rename: from to: to Sealed source

Rename or move a file or directory (class method).

Returns Result ok: nil on success, or Result error: err on failure.

Examples

File rename: "old.txt" to: "new.txt"

absolutePath: path Sealed source

Resolve a relative path to its absolute path (class method).

Returns Result ok: absPath on success, or Result error: err on failure.

Examples

File absolutePath: "target/test.txt"

cwd Sealed source

Return the current working directory (class method).

Examples

File cwd   // => "/home/user/projects/myapp"

tempDirectory Sealed source

Return the OS temporary directory path (class method).

Examples

File tempDirectory

Inherited Methods

From Object

class

Return the class of the receiver.

Examples

42 class              // => Integer
"hello" class         // => String

isNil

Test if the receiver is nil. Returns false for all objects except nil.

Examples

42 isNil              // => false
nil isNil             // => true

notNil

Test if the receiver is not nil. Returns true for all objects except nil.

Examples

42 notNil             // => true
nil notNil            // => false

ifNil: _nilBlock

If the receiver is nil, evaluate nilBlock. Otherwise return self.

Examples

42 ifNil: [0]         // => 42
nil ifNil: [0]        // => 0

ifNotNil: notNilBlock

If the receiver is not nil, evaluate notNilBlock with self.

Examples

42 ifNotNil: [:v | v + 1]   // => 43
nil ifNotNil: [:v | v + 1]  // => nil

ifNil: _nilBlock ifNotNil: notNilBlock

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

ifNotNil: notNilBlock ifNil: _nilBlock

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

printString

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"

displayString

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"

inspect

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)

yourself Sealed

Return the receiver itself. Useful for cascading side effects.

Examples

42 yourself            // => 42

hash

Return a hash value for the receiver.

Examples

42 hash

respondsTo: selector Sealed

Test if the receiver responds to the given selector.

Examples

42 respondsTo: #abs    // => true

fieldNames Sealed

Return the names of fields.

Examples

42 fieldNames             // => #()

fieldAt: name Sealed

Return the value of the named field.

Examples

object fieldAt: #name

fieldAt: name put: value Sealed

Set the value of the named field (returns new state).

Examples

object fieldAt: #name put: "Alice"

perform: selector Sealed

Send a unary message dynamically.

Examples

42 perform: #abs       // => 42

perform: selector withArguments: args Sealed

Send a message dynamically with arguments.

Examples

3 perform: #max: withArguments: #(5)   // => 5

subclassResponsibility

Raise an error indicating this method must be overridden by a subclass.

Examples

self subclassResponsibility

notImplemented

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

show: aValue

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: "

showCr: aValue

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"

isKindOf: aClass

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)

error: message

Raise an error with the given message.

Examples

self error: "something went wrong"

delegate Sealed

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

== other

Test value equality (Erlang ==).

Examples

42 == 42           // => true
"abc" == "abc"     // => true

/= other

Test value inequality (negation of ==).

Examples

1 /= 2             // => true
42 /= 42           // => false

class

Return the class of the receiver.

Examples

42 class            // => Integer
"hello" class       // => String

doesNotUnderstand: selector args: arguments

Handle messages the receiver does not understand. Override for custom dispatch.

Examples

42 unknownMessage   // => ERROR: does_not_understand

perform: selector withArguments: arguments

Send a message dynamically with an arguments list.

Examples

42 perform: #abs withArguments: #()   // => 42

performLocally: selector withArguments: arguments

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)

perform: selector withArguments: arguments timeout: timeoutMs

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