Feature #15563
Updated by 3limin4t0r (Johan Wentholt) almost 6 years ago
Ruby 2.3.0 introduced `#dig` for *Array*, *Hash* and *Struct*. Both *Array* and *Hash* have `#fetch` which does the same as `#[]`, but instead of returning the default value an exception is raised (unless a second argument or block is given). *Hash* also has `#fetch_values` which does the same as `#values_at`, raising an exception if an key is missing. For `#dig` there is no such option.
My proposal is to add a method which does the same as `#dig`, but instead of using the `#[]` accessor it uses `#fetch`.
This method would look something like this:
```Ruby
module DigWithException
def dig_e(key, *others)
value = fetch(key)
return value if value.nil? || others.empty?
if value.respond_to?(__method__, true) value.respond_to?(__method__)
value.send(__method__, value.public_send(__method__, *others)
else
raise TypeError, "#{value.class} does not have ##{__method__} method"
end
end
end
Array.include(DigWithException)
Hash.include(DigWithException)
```
The exception raised is also taken from `#dig` (`[1].dig(0, 1) #=> TypeError: Integer does not have #dig method`). I personally have my issues with the name `#dig_e`, but I haven't found a better name yet.
There are also a few other things that I haven't thought out yet.
1. Should this method be able to accept a block which, will be passed to the `#fetch` call and recursive `#dig_e` calls?
```Ruby
module DigWithException
def dig_e(key, *others, &block)
value = fetch(key, &block)
return value if value.nil? || others.empty?
if value.respond_to?(__method__, true) value.respond_to?(__method__)
value.send(__method__, value.public_send(__method__, *others, &block)
else
raise TypeError, "#{value.class} does not have ##{__method__} method"
end
end
end
Array.include(DigWithException)
Hash.include(DigWithException)
```
2. I currently kept the code compatible with the `#dig` description.
> Extracts the nested value specified by the sequence of *key* objects by calling `dig` at each step, returning `nil` if any intermediate step is `nil`.
However, with this new version of the method one could consider dropping the *"returning `nil` if any intermediate step is `nil`"* part, since this would be the more strict version.
```Ruby
module DigWithException
def dig_e(key, *others)
value = fetch(key)
return value if others.empty?
if value.respond_to?(__method__, true) value.respond_to?(__method__)
value.send(__method__, value.public_send(__method__, *others)
else
raise TypeError, "#{value.class} does not have ##{__method__} method"
end
end
end
Array.include(DigWithException)
Hash.include(DigWithException)
```
I'm curious to hear what you guys think about the idea as a whole, the method name and the two points described above.