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A subtle difference between Ruby's Hash.fetch(:key, :default) vs. (Hash[:key] || :default)
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| h = { | |
| 'a' => :a_value, | |
| 'b' => nil, | |
| 'c' => false | |
| } | |
| h.fetch('a', :default_value) #=> :a_value | |
| h.fetch('b', :default_value) #=> nil | |
| h.fetch('c', :default_value) #=> false | |
| h.fetch('d', :default_value) #=> :default_value | |
| (h['a'] || :default_value) #=> :a_value | |
| (h['b'] || :default_value) #=> :default_value | |
| (h['c'] || :default_value) #=> :default_value | |
| (h['d'] || :default_value) #=> :default_value |
Why use
fetchif default value is not returned andnilcan blow the application up? I'm now confused
fetch does return a default value, presuming you provide one. You can also provide a block, the return value of which, will be used as the "default value" in the case the key is missing from the hash.
You can get exactly same result if you do Hash.fetch(:key, ::default_value) || :default_value.
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Why use
fetchif default value is not returned andnilcan blow the application up? I'm now confused