[#107008] [Ruby master Bug#18465] Make `IO#write` atomic. — "ioquatix (Samuel Williams)" <noreply@...>
Issue #18465 has been reported by ioquatix (Samuel Williams).
16 messages
2022/01/09
[#107150] [Ruby master Feature#18494] [RFC] ENV["RUBY_GC_..."]= changes GC parameters dynamically — "ko1 (Koichi Sasada)" <noreply@...>
Issue #18494 has been updated by ko1 (Koichi Sasada).
4 messages
2022/01/17
[#107170] Re: [Ruby master Feature#18494] [RFC] ENV["RUBY_GC_..."]= changes GC parameters dynamically
— Eric Wong <normalperson@...>
2022/01/17
> https://bugs.ruby-lang.org/issues/18494
[#107302] [Ruby master Bug#18553] Memory leak on compiling method call with kwargs — "ibylich (Ilya Bylich)" <noreply@...>
Issue #18553 has been reported by ibylich (Ilya Bylich).
4 messages
2022/01/27
[#107346] [Ruby master Misc#18557] DevMeeting-2022-02-17 — "mame (Yusuke Endoh)" <noreply@...>
Issue #18557 has been reported by mame (Yusuke Endoh).
18 messages
2022/01/29
[ruby-core:107366] [Ruby master Feature#16122] Struct::Value: simple immutable value object
From:
"matheusrich (Matheus Richard)" <noreply@...>
Date:
2022-01-30 20:39:06 UTC
List:
ruby-core #107366
Issue #16122 has been updated by matheusrich (Matheus Richard).
Some more alternative to get the ideas rolling: `Unit` and `Item` (might be paired with Struct)
I also like `Box`.
----------------------------------------
Feature #16122: Struct::Value: simple immutable value object
https://bugs.ruby-lang.org/issues/16122#change-96267
* Author: zverok (Victor Shepelev)
* Status: Feedback
* Priority: Normal
----------------------------------------
**Value Object** is a useful concept, introduced by Martin Fowler ([his post](https://martinfowler.com/bliki/ValueObject.html), [Wikipedia Entry](https://en.wikipedia.org/wiki/Value_object)) with the following properties (simplifying the idea):
* representing some relatively simple data;
* immutable;
* compared by type & value;
* nicely represented.
Value objects are super-useful especially for defining APIs, their input/return values. Recently, there were some movement towards using more immutability-friendly approach in Ruby programming, leading to creating several discussions/libraries with value objects. For example, [Tom Dalling's gem](https://github.com/tomdalling/value_semantics), [Good Ruby Value object convention](https://github.com/zverok/good-value-object) (disclaimer: the latter is maintained by yours truly).
I propose to introduce **native value objects** to Ruby as a core class.
**Why not a gem?**
* I believe that concept is that simple, that nobody *will even try* to use a gem for representing it with, unless the framework/library used already provides one.
* Potentially, a lot of standard library (and probably even core) APIs could benefit from the concept.
**Why `Struct` is not enough**
Core `Struct` class is "somewhat alike" value-object, and frequently used instead of one: it is compared by value and consists of simple attributes. On the other hand, `Struct` is:
* mutable;
* collection-alike (defines `to_a` and is `Enumerable`);
* dictionary-alike (has `[]` and `.values` methods).
The above traits somehow erodes the semantics, making code less clear, especially when duck-typing is used.
For example, this code snippet shows why `to_a` is problematic:
```ruby
Result = Struct.new(:success, :content)
# Now, imagine that other code assumes `data` could be either Result, or [Result, Result, Result]
# So, ...
data = Result.new(true, 'it is awesome')
Array(data) # => expected [Result(true, 'it is awesome')], got [true, 'it is awesome']
# or...
def foo(arg1, arg2 = nil)
p arg1, arg2
end
foo(*data) # => expected [Result(true, 'it is awesome'), nil], got [true, 'it is awesome']
```
Having `[]` and `each` defined on something that is thought as "just value" can also lead to subtle bugs, when some method checks "if the received argument is collection-alike", and value object's author doesn't thought of it as a collection.
**Concrete proposal**
* Class name: `Struct::Value`: lot of Rubyists are used to have `Struct` as a quick "something-like-value" drop-in, so alternative, more strict implementation, being part of `Struct` API, will be quite discoverable; *alternative: just `Value`*
* Class API is copying `Struct`s one (most of the time -- even reuses the implementation), with the following exceptions *(note: the immutability is **not** the only difference)*:
* Not `Enumerable`;
* Immutable;
* Doesn't think of itself as "almost hash" (doesn't have `to_a`, `values` and `[]` methods);
* Can have empty members list (fun fact: `Struct.new('Foo')` creating member-less `Struct::Foo`, is allowed, but `Struct.new()` is not) to allow usage patterns like:
```ruby
class MyService
Success = Struct::Value.new(:results)
NotFound = Struct::Value.new
end
```
`NotFound` here, unlike, say, `Object.new.freeze` (another pattern for creating "empty typed value object"), has nice inspect `#<value NotFound>`, and created consistently with the `Success`, making the code more readable. And if it will evolve to have some attributes, the code change would be easy.
**Patch is provided**
[Sample rendered RDoc documentation](https://zverok.github.io/ruby-rdoc/Struct-Value.html)
---Files--------------------------------
struct_value.patch (18.6 KB)
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