About Ruby's conversion method pairs

Ruby has a set of methods to convert an object to another representation. Most of them come in explicit and implicit flavor.

explicit implicit
to_a to_ary
to_h to_hash
to_s to_str
to_i to_int

There may be even more.

Don't name your methods like the implicit version (most prominently to_hash) but the like the explicit one.

Explicit conversion

Explicit conversion happens when requesting it, e.g. with the splat operator:

args = [1,2,3]
some_method(*args) # Ruby calls args.to_a here

Implicit conversion

Implicit conversion happens when Ruby tries to convert an object when it thinks it should:

args = [1,2,3]
a, b, c = args # Ruby calls args.to_ary here

# Fictional example; Ruby decomposes the block argument by calling args.to_ary
[args].each do |(x, y, z)| puts x, y, z; end

Obviously, this is the reason behind this recent card about Ruby implicitly converting a hash to keyword arguments. It's not a bug, it's a feature!

Also see the linked Stackoverflow post.

Dominik Schöler over 5 years ago
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