From: "cb341 (Daniel Bengl) via ruby-core" <ruby-core@...>
Date: 2025-08-26T06:39:08+00:00
Subject: [ruby-core:123074] [Ruby Feature#21545] #try_dig, a dig that returns early if it cannot dig deeper

Issue #21545 has been updated by cb341 (Daniel Bengl).


herwin (Herwin W) wrote in #note-7:
> Maybe I'm reading too much into the examples, but this looks to me like something where pattern matching would be more suitable:
> 
> ```ruby
> def match(input)
>   case input
>   in { status: { code: Integer => status } }
>     puts "Status code: #{status}"
>   in { status: status }
>     puts "Other status: #{status}"
>   else
>     raise "mismatch: #{input}"
>   end
> end
> 
> match({ status: "ok" })
> match({ status: { code: 200 } })
> ```
> 
> Output:
> ```
> Other status: ok
> Status code: 200
> ```

This is a beautiful solution to the API problem. I see how this can be better than `try_dig` as you can explicitly match all formats you want to handle and group the rest.
Instead of raising you could also return nil if you only care about the data if it is present and don't care about edge cases.

----------------------------------------
Feature #21545: #try_dig, a dig that returns early if it cannot dig deeper
https://bugs.ruby-lang.org/issues/21545#change-114387

* Author: cb341 (Daniel Bengl)
* Status: Open
----------------------------------------
Ruby offers `dig` for traversing nested hashes and arrays. It is strict and will raise if an intermediary object does not support `dig`. In many cases we only want to attempt the lookup and return `nil` if it cannot be followed, without caring about the exact reason.

**Example:**

```rb
{ a: "foo" }.dig(:a, :b)
# TypeError: String does not have #dig method

{ a: "foo" }.try_dig(:a, :b)
# => nil
```

This is especially useful when dealing with data from APIs or other inconsistent sources:

```rb
api_response = { status: "ok" }
api_response.try_dig(:status, :code) # => nil

api_response = { status: { code: 200 } }
api_response.try_dig(:status, :code) # => 200
```

The name `try_dig` makes it clear that it behaves like `dig` but will never raise for structural mismatches.  
It complements `dig` and the proposed `dig!` ([#12282](https://bugs.ruby-lang.org/issues/12282), [#15563](https://bugs.ruby-lang.org/issues/15563)) by covering the tolerant lookup case.

A possible sketch:

```rb
class Object
  def try_dig(*path)
    current = self
    path.each do |key|
      return nil unless current.respond_to?(:dig)
      begin
        current = current.dig(key)
      rescue StandardError
        return nil
      end
    end
    current
  end
end
```

_I initially proposed this in Ruby core ([PR #14203](https://github.com/ruby/ruby/pull/14203)) and even implemented it in C, but later realized that if this gets introduced at all it probably makes more sense to have it in ActiveSupport rather than in core Ruby._

**Advantages**
  - Simplifies tolerant lookups without repetitive rescue logic  
  - Clear intent when the value is optional  
  - Useful for working with inconsistent or partially known data structures  
  - Complements `dig` and potential `dig!` by covering the tolerant case  

**Disatvantages**
  - May hide structural issues that should be noticed during development





-- 
https://bugs.ruby-lang.org/
______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
 ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/