代码布局

Ruby 中的表达式以换行符分隔

x = 1
y = 2
z = x + y

换行符也用作某些控制结构标题与其主体之间的逻辑分隔符

if z > 3       # line break ends the condition and starts the body
  puts "more"
end

while x < 3    # line break ends the condition and starts the body
  x += 1
end

; 可用作表达式分隔符，代替换行符

x = 1; y = 2; z = x + y
if z > 3; puts "more"; end

传统上，以 ; 分隔的表达式仅用于短脚本和实验。

在某些控制结构中，有一个可选关键字，可以用来分隔其元素，而不是使用换行符

# if, elsif, until and case ... when: 'then' is an optional separator:

if z > 3 then puts "more" end

case x
when Numeric then "number"
when String then "string"
else "object"
end

# while and until: 'do' is an optional separator
while x < 3 do x +=1 end

此外，在某些不会造成歧义的地方可以省略换行符。请注意上面的示例：end 前不需要换行符，就像 else 后不需要换行符一样。

在行中断表达式

一个表达式可能被分成几行，当每一行都可以明确地识别为“不完整”而没有下一行时。

这些可以正常工作

x =         # incomplete without something after =
    1 +     # incomplete without something after +
    2

File.read "test.txt",         # incomplete without something after ,
          enconding: "utf-8"

这些将无法工作

# unintended interpretation:
x = 1     # already complete expression
    + 2   # interpreted as a separate +2

# syntax error:
File.read "test.txt"           # already complete expression
          , encoding: "utf-8"  # attempt to parse as a new expression, SyntaxError

规则的例外情况是，以 .（“前导点”风格的方法调用）或逻辑运算符 &&/|| 和 and/or 开头的行

# OK, interpreted as a chain of calls
File.read('test.txt')
    .strip("\n")
    .split("\t")
    .sort

# OK, interpreted as a chain of logical operators:
File.empty?('test.txt')
  || File.size('test.txt') < 10
  || File.read('test.txt').strip.empty?

如果表达式以上述任何方式拆分成多行，则允许在单独的行之间插入注释

sum = base_salary +
      # see "yearly bonuses section"
      yearly_bonus(year) +
      # per-employee coefficient is described
      # in another module
      personal_coeff(employee)

# We want to short-circuit on empty files
File.empty?('test.txt')
  # Or almost empty ones
  || File.size('test.txt') < 10
  # Otherwise we check if it is full of spaces
  || File.read('test.txt').strip.empty?

最后，代码可以通过 \ 显式告知 Ruby 该表达式将继续到下一行

# Unusual, but works
File.read "test.txt" \
          , encoding: "utf-8"

# More regular usage (joins the strings on parsing instead
# of concatenating them in runtime, as + would do):
TEXT = "One pretty long line" \
       "one more long line" \
       "one other line of the text"

\ 在解析时充当换行符转义，因此不能在它们之间插入注释

TEXT = "line 1" \
       # here would be line 2:
       "line 2"

# This is interpreted as if there was no line break where \ is,
# i.e. the same as
TEXT = "line 1" # here would be line 2:
       "line 2"

puts TEXT #=> "line 1"