UPDATE: Most of the advice in this post is superceded by the followup which reflects the best solution for default hash values.
If you ever find yourself writing initialization for ruby hash values that looks something like this:
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You can save yourself the
||= statement by initializing your hash with a default value.
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One small caveat is that accessing a hash at an unknown key will return
the exact instance that you gave to your
Hash initializer. If it's a mutable object
such as the
Array in this example, then mutating the object for an unknown key
will change the value for ALL unknown keys.
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So go forth and use default hash values! Just be mindful to avoid changes to the default value object.
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As you can see there is still a potential bug lurking above where we never actually assign a value to the hash key, however instead of returning a mutated instance for missing values what you get is the result of evaluating the block that is passed into the hash initializer.
In the scheme of things this is a better solution for initializing a hash with a default value since the default will never get polluted by accidental mutations on the default object.