From: konstantin@...
Date: 2018-03-08T11:59:37+00:00
Subject: [ruby-core:86049] [Ruby trunk Feature#14580] Hash#store accepts a	block

Issue #14580 has been updated by Soilent (Konstantin x).


Eregon (Benoit Daloze) wrote:
> Soilent (Konstantin x) wrote:
> > Consider another example `hash.store(:time) { |ts| Time.parse(ts) }`
> 
> That looks weird to me.
> Either the Hash is caching String to Time, and then it should use
> 
> ~~~ruby
> Hash.new { |h,k| h[k] = Time.parse(k) }
> ~~~
> 
> or it contains other data and then there seems to be little reason to first store a String for key :time and then only later parse it to a Time instance.

I see your point, but the example was not about String to Time caching. Let's say you receive an HTTP POST request with the body `timestamp=2018-03-08T11:24:44Z&temperature=27`. You might want to validate the request and store it in a database:

~~~ruby
begin
  params.store(:temperature) { |tm| Integer(tm) }
  params.store(:timestamp) { |ts| Time.parse(ts) }
rescue ArgumentError => err
  # Invalid request, send response with status 422 or 400
end

# Do something with `params`

db[:events].insert(params)
~~~

I think that Hash#store with a block arg looks quite natural with the rest of the methods from the Hash API.

----------------------------------------
Feature #14580: Hash#store accepts a block
https://bugs.ruby-lang.org/issues/14580#change-70913

* Author: Soilent (Konstantin x)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Given a hash

~~~ ruby
hash = { a: 2 }
~~~

I want to update a single value in the hash:

~~~ ruby
hash[:a] = hash[:a] + 42
hash[:a] #=> 44
~~~

But instead, I would like to have a method that yields the current value for a given key and associates the block result with the key (similar to Hash#update). I think that Hash#store can be extended to support a block arg.

~~~ ruby
hash.store(:a) { |val| val + 42 }
hash[:a] #=> 44
~~~

Or it can be something like this:

~~~ ruby
hash.transform_values(:a, :b) { |val| val + 42 }
hash[:a] #=> 44
~~~



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