Rename hash keys

Hash#fetch is a great way to ensure that a hash key is present. The error message when a key is missing though is rather useless if you don't have immediate access to the object and want to debug why keys are missing, e.g. in the parsed JSON res...

The NestedHash class allows you to read and write hashes of any depth. Examples:

hash = {}
NestedHash.write hash, 'a', 'b', 'c', 'value' # => { a: { b: { c: 'value' } } }
NestedHash.read hash, 'a', 'b', 'c' # => 'value'
NestedHash.read hash...

There are many different methods that allow mapping an Array to a Hash in Ruby.

Array#to_h with a block (Ruby 2.6+)

You can call an array with a block that is called with each element. The block must return a [key, value] tuple.

This i...

When a method has keyword arguments, Ruby offers implicit conversion of a Hash argument into keyword arguments. This conversion is perfo...

tl;dr: Do not use merge! for session hashes. Use update instead.

Outline

Let's assume you're modifying the Rails session. For simplicity, let's also assume your session is empty when you start (same effect when there is data):

# In o...

The attached initializer gives your hashes a #deep_slice method that lets you recursively slice their contents by a given whitelist of allowed keys and sub-keys:

{ :a => { ...

Rails flashes (FlashHash) track a list of used keys, which is not respected when comparing flash hashes.

This does not concern you under most circumstances.

Basics

When ActionController picks up a flash object, it will call the #sweep m...

In production, you (or your ops team) should configure a maximum number of bytes that Redis can use to store data (maxmemory setting).
They may even want to set maxmemory-policy to noeviction to avoid keys being removed that you want to keep...

To test whether a hash includes an expected sub-hash:

expect(user.attributes).to match(hash_including('name' => 'Bruce Wayne'))
expect(User).to receive(:create!).with(hash_including('name' => 'Bruce Wayne'))

If you parse this Yaml ...

yes: 'Totally'
no: 'Nope'

... you get this Ruby hash:

{ true: 'Totally',
  false: 'Nope' }

In order to use the strings 'yes' and 'no' as keys, you need to wrap them with quotes:

'yes'...