Module: Ks
- Defined in:
- lib/ks.rb
Overview
“Ks” - as in “kiss” - a generator of keyworded Structs.
Constant Summary collapse
- VERSION =
'0.0.2'
- @@caching_mutex =
Mutex.new
- @@predefined_structs =
{}
Class Method Summary collapse
-
.allowing_unknown(*members) ⇒ Object
Returns a class that is a descendant of Struct, with a keyword initializer that permits unknown keywords to be passed in.
-
.strict(*members) ⇒ Object
Returns a class that is a descendant of Struct, with a strict keyword initializer.
Class Method Details
.allowing_unknown(*members) ⇒ Object
Returns a class that is a descendant of Struct, with a keyword initializer that permits unknown keywords to be passed in. Those keywords will be dropped. The keywords that are known at definition time will be checked for presence. This allows you to use structs for API responses and payloads that might get additional properties as the API evolves, without breaking (your) consuming code. Imagine at time of designing your structures you specify a Shipment:
Shipment = Ks.allowing_unknown(:sku, :weight)
The API you are using, however, later adds a “shipping_company_id” property. If you had used ‘strict` your struct would fail to initialize, since it does not know about the `shipping_company_id` attribute.
Shipment.new(JSON.parse(payload)) #=> ArgumentError...
but as you have used ‘allowing_unknown` the “shipping_company_id” property will be silently dropped instead.
The created classes (Struct descendants) are cached to make reloading easier, since when reloading a usual Struct descendant it will receive a different parent class. This is mitigated by caching the created subclasses using their member lists
73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 |
# File 'lib/ks.rb', line 73 def self.allowing_unknown(*members) k = 'with_optionals:' + members.sort.join(':') @@caching_mutex.synchronize do return @@predefined_structs[k] if @@predefined_structs[k] struct_ancestor = Struct.new(*members) predefined = Class.new(struct_ancestor) do class_eval <<-METHOD, __FILE__, __LINE__ + 1 def initialize(#{members.map { |a| "#{a}:" }.join(', ')}, **) # def initialize(bar:, baz:, **) super(#{members.join(', ')}) # super(bar, baz) end # end METHOD end @@predefined_structs[k] = predefined predefined end end |
.strict(*members) ⇒ Object
Returns a class that is a descendant of Struct, with a strict keyword initializer.
Info = Ks.strict(:item_count, :weight)
data = Info.new(item_count: 1, weight: 2)
Note that all the keyword arguments defined for the class (all the members) are going to be required keyword arguments for the initializer.
The created classes (Struct descendants) are cached to make reloading easier, since when reloading a usual Struct descendant it will receive a different parent class. This is mitigated by caching the created subclasses using their member lists
28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 |
# File 'lib/ks.rb', line 28 def self.strict(*members) k = members.sort.join(':') @@caching_mutex.synchronize do return @@predefined_structs[k] if @@predefined_structs[k] struct_ancestor = Struct.new(*members) predefined = Class.new(struct_ancestor) do class_eval <<-METHOD, __FILE__, __LINE__ + 1 def initialize(#{members.map { |a| "#{a}:" }.join(', ')}) # def initialize(bar:, baz:) super(#{members.join(', ')}) # super(bar, baz) end # end METHOD end @@predefined_structs[k] = predefined predefined end end |