To_do or not_to_do that_is_the_question? Ruby logic control flow guide

What we know about logic in ruby?

Logic operators: (by priority) ! && || not and, or

What we know about control flow in ruby?

Control flow: ?: if unless

Hmm. Interesting, how we can to relate this parts?

Let`s see foo = 42 && foo / 2 foo = 42 and foo / 2

Let`s see foo = 42 && foo / 2 foo = 42 and foo / 2 NoMethodError: undefined method `/' for nil:NilClass 21

Help methods def to_do puts ‘What to do?’ end def not_to_do puts ‘Nothing to do’ end def that_is_the_question?(question = false) question end

When we are lazy job = that_is_the_question? job or not_to_do # => ‘Noting to do’ job || not_to_do # => ‘Noting to do’

When we are lazy job or not_to_do # => ‘Noting to do’ job || not_to_do # => ‘Noting to do’ job or puts ‘Noting to do’ # => ‘Noting to do’ job || puts ‘Noting to do’ # => syntax error, unexpected tSTRING_BEG, expecting kDO or '{' or '(' job || puts 'Noting to do' job = that_is_the_question?

The solution for control flow with ‘||’ is to place action in parentheses job || (puts ‘Noting to do’)

The same situation when we a hard-working job = that_is_the_question? ‘of course’ job and to_do # => ‘What to do?’ job && to_do # => ‘What to do?’ job and puts ‘What to do?’ # => ‘What to do? job && puts ‘Noting to do’ # => syntax error, unexpected tSTRING_BEG, expecting kDO or '{' or '(' job || puts 'Noting to do' But now we know, how to fix this

Control flow practice if job to_do end unless job not_to_do end to_do if job not_to_do unless job

Control flow practice if job to_do end unless job not_to_do end to_do if job not_to_do unless job job and to_do job or not_to_do job or raise ‘LAZY boy’

Control flow practice if job to_do end unless job not_to_do end to_do if job not_to_do unless job job and to_do job or not_to_do job or raise ‘LAZY boy’ Control flow with logic operators

1 || 2 && nil 1 or 2 and nil Some kind of magic

1 || 2 && nil # => 1 1 or 2 and nil # => nil Some kind of magic

No content

1 || 2 && nil # => 1 1 or 2 and nil # => nil Some kind of magic Higher priority Lower priority

They are the same, but so different

What we have? use ‘&&’ and ‘||’ only for logic flow use ‘and’ and ‘or’ only for control flow Golden rule:

And something else Always use regimented code style https:/ /github.com/styleguide/ruby https:/ /github.com/bbatsov/ruby-style-guide

Ruby rocks!

Thanks for your attention