TL;DR {} binds stronger than do … end (as always in Ruby, special characters bind stronger than words)
Demo
✔️ Right way
names = ['bRUce', 'STaN', 'JOlIE']
# Blocks in braces are passed to the rightmost method
print names.map { |name| name.downcase }
print(names.map do |name| name.downcase end) # equivalent
=> ["bruce", "stan", "jolie"]
❌ Wrong way
Avoid the examples below, as you pass at least one block to print and not to the enumerator.
names = ['bRUce', 'STaN', 'JOlIE']
# Blocks in do…end are passed to the leftmost method
print names.map do |name| name.downcase end
print(names.map) { |name| name.downcase } # equivalent
=> #<Enumerator:0x00000001e793b0>
# Combined
print names.map { |name| name.downcase } do |name| name.capitalize end
print(names.map { |name| name.downcase }) do |name| name.capitalize end # equivalent
=> ["bruce", "stan", "jolie"]
Posted by Henning Koch to makandra dev (2012-04-05 09:11)