＃{...}是什么意思？

Question

如从为什么的凄美指南下面的代码：

def wipe_mutterings_from(sentence) 
    unless sentence.respond_to? :include? 
     raise ArgumentError, "cannot wipe mutterings from a #{ sentence.class }" 
    end 
    while sentence.include? '(' 
     open = sentence.index('(') 
     close = sentence.index(')', open) 
     sentence[open..close] = '' if close 
    end 
end 

Answer 1

在一个Ruby双引号字符串 - 包括字符串文字等s = "…"和s = %Q{ ... }和s = <<ENDCODE-语法#{ … }用于“字符串插值”，将动态内容插入到字符串中。例如：

i = 42 
s = "I have #{ i } cats!" 
#=> "I have 42 cats!" 

它等同于（而且更方便比有效）使用字符串连接用显式调用to_s沿：

i = 42 
s= "I have " + i.to_s + " cats!" 
#=> "I have 42 cats!" 

您可以将任意代码的区域内，包括多行上的多个表达式。评估代码的最终结果已呼吁其to_s，以确保它是一个字符串值：

"I've seen #{ 
    i = 10 
    5.times{ i+=1 } 
    i*2 
} weasels in my life" 
#=> "I've seen 30 weasels in my life" 

[4,3,2,1,"no"].each do |legs| 
    puts "The frog has #{legs} leg#{:s if legs!=1}" 
end 
#=> The frog has 4 legs 
#=> The frog has 3 legs 
#=> The frog has 2 legs 
#=> The frog has 1 leg 
#=> The frog has no legs 

---

注意，这有单引号字符串里面没有任何影响：

s = "The answer is #{6*7}" #=> "The answer is 42" 
s = 'The answer is #{6*7}' #=> "The answer is #{6*7}" 

s = %Q[The answer is #{ 6*7 }] #=> "The answer is 42" 
s = %q[The answer is #{ 6*7 }] #=> "The answer is #{6*7}" 

s = <<ENDSTRING 
The answer is #{6*7} 
ENDSTRING 
#=> "The answer is 42\n" 

s = <<'ENDSTRING' 
The answer is #{6*7} 
ENDSTRING 
#=> "The answer is #{6*7}\n" 

---

为了方便起见，如果您只想插入实例变量（@foo），全局变量的值，则可以选择用于字符串插值的{}字符变量（$foo），或类变量（@@foo）：

@cats = 17 
s1 = "There are #{@cats} cats" #=> "There are 17 cats" 
s2 = "There are #@cats cats" #=> "There are 17 cats" 

Answer 2

"#{}"意味着在Ruby中的字符串interpolation.See Here太多的答案。

Answer 3

#{}用于Ruby插值。在这个例子中，

这将提高一个ArgumentError与该消息，

cannot wipe mutterings from a <whatever sentence.class evaluates to>

这是一个有用的读 - String concatenation vs. interpolation in Ruby