RubyData.define (Ruby 3.2+) tạo immutable value object — khác Struct ở chỗ mọi attribute đều read-only và object được freeze sau initialize.
ruby
# Struct — mutable
Point = Struct.new(:x, :y)
p = Point.new(1, 2)
p.x = 99 # OK — Struct cho phép gán
# Data.define — immutable
Coord = Data.define(:lat, :lng)
c = Coord.new(lat: 10.0, lng: 106.0)
c.lat # => 10.0
c.lat = 99 # => NoMethodError — no setter
c.frozen? # => true
# Tạo bản mới với 1 trường thay đổi
c2 = c.with(lat: 21.0)
c2.lng # => 106.0 — lng giữ nguyênStruct | Data.define | |
|---|---|---|
| Mutability | Mutable (có setter) | Immutable (frozen) |
with method | Không | Có |
| Dùng cho | Value object + behavior đơn giản | Pure value object (DTO, event) |
Data.define là lựa chọn tốt hơn Struct cho domain object thuần dữ liệu (Money, Coordinate, DateRange, API response).
Data.define (Ruby 3.2+) creates an immutable value object — unlike Struct, all attributes are read-only and the object is frozen after initialization.
ruby
# Struct — mutable
Point = Struct.new(:x, :y)
p = Point.new(1, 2)
p.x = 99 # OK
# Data.define — immutable
Coord = Data.define(:lat, :lng)
c = Coord.new(lat: 10.0, lng: 106.0)
c.lat # => 10.0
c.lat = 99 # => NoMethodError
c.frozen? # => true
# Create a new instance with one field changed
c2 = c.with(lat: 21.0)
c2.lng # => 106.0 — unchangedStruct | Data.define | |
|---|---|---|
| Mutability | Mutable (has setters) | Immutable (frozen) |
with method | No | Yes |
| Best for | Value objects + simple behaviour | Pure value objects (DTO, event) |
Data.define is the better choice for domain objects that carry only data (Money, Coordinate, DateRange, API response).