next versus if in a .each loop?

Question

I have a text processing thing I'm doing in Ruby. Basically, I have to implement a simple state machine (with one character look-behind).

My code at the moment looks like this:

text.each{ |c|   ...   ...   ...   ...   if @state!=:some_state     next   end   #processing stuff for if in :some_state mode   ...   ...   ...   ...   ... } 

Is this proper? Or should it rather be implemented like:

text.each{ |c|   ...   ...   ...   ...   if @state==:some_state     #processing stuff for if in :some_state mode     ...     ...     ...     ...     ...   end } 

Is there a right way or is it just preference? Which one blends more with "the ruby way" of doing things?

Answer 1

Totally agree with @DigitalRoss and I have seen people using next if there is complicated piece of code after some condition is being evaluated i.e.

 next if @state!=:some_state  # some long complicated code 

on the other hand if there is a simple operation that needs to be performed on the basis of some condition then I would prefer

 if @state == :some_state    #call_a_method_to_do_something  end   OR   call_a_method if @state == :some_state 

Having said that, its bad practice to write long complicated code. If your code is clean and well designed then you would never have to use next within your code.

Answer 2

I think that the example you gave doesn't really capture situation where doing next makes a difference. Consider the situation where you have multiple "next-points" in your code:

text.each do |c|   next if @state == :state1   ...   next if @state == :state2   ...   next if @state == :state3   ... end 

and compare it with if-variant:

text.each do |c|   unless @state == :state1     ...     unless @state == :state2       ...       unless @state == :state3         ...       end     end   end end 

Although the first could be viewed as spaghetti-style by some purists, IMHO it is more readable than the latter.