娃娃鸭学Ruby-27、Unless

Unless
unless,作为一个语句或修饰符，和if恰好相反：当且仅当与其关联的表达式的值为false或nil，它才会执行相应的代码。

unless condition
code
end

unless condition
  code
else
code
end

s=unless o.nil?
  o.to_s
end
s=unless o.nil? then o.to_s end

unless x==0
  puts "x is not 0"
else
  unless y==0
    puts "y is not 0"
  else
    unless z==0
       puts "z is not 0"
    else
      puts "all are 0"
    end
end
end

2011-4-17 16:54 danny