Ruby-字符串

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Ruby将字符串像数字一样处理.我们用单引号('...')或双引号("...")将它们括起来.

ruby> "abc"

  "abc"

ruby> 'abc'

  "abc" 

单引号和双引号在某些情况下有不同的作用.一个由双引号括起来的字符串允许使用转义字符，就是反斜杠开头的字符，而且可以用#{}内嵌表达式.而单引号括起来的字符串并不会对字符串作任何解释;你看到的是什么便是什么.几个例子:

ruby> print "a\nb\nc","\n"

a

b

c

  nil

ruby> print 'a\nb\n',"\n"

a\nb\nc

  nil

ruby> "\n"

  "\n"

ruby> '\n'

  "\\n"

ruby> "\001"

  "\001"

ruby> '\001'

  "\\001"

ruby> "abcd #{5*3} efg"

  "abcd 15 efg"

ruby> var = " abc "

  " abc "

ruby> "1234#{var}5678"

  "1234 abc 5678" 

Ruby的字符串操作比C更灵巧,更直观.比如说,你可以用+把几个串连起来,用*把一个串重复好几遍:

ruby> "foo" + "bar"

  "foobar"

ruby> "foo" * 2

  "foofoo" 

相比之下,在C里,因为需要精确的内存管理,串联字符串要笨拙的多:

char *s = malloc(strlen(s1)+strlen(s2)+1);

strcpy(s, s1);

strcat(s, s2);

/* ... */

free(s); 

但对于Ruby,我们不需要考虑字符串的空间占用问题,这令到我们可以从烦琐的内存管理中解脱出来.

下面是一些字符串的处理,

串联:

ruby> word = "fo" + "o"

  "foo" 

重复:

ruby> word = word * 2

  "foofoo"  

抽取字符(注意:在Ruby里,字符被视为整数):

ruby> word[0]

  102            # 102 is ASCII code of `f' 

ruby> word[-1]

  111            # 111 is ASCII code of `o'  

(负的索引指从字符串尾算起的偏移量,而不是从串头.)

提取子串:

ruby> herb = "parsley"

  "parsley"

ruby> herb[0,1]

  "p"

ruby> herb[-2,2]

  "ey"

ruby> herb[0..3]

  "pars"

ruby> herb[-5..-2]

  "rsle"  

检查相等:

ruby> "foo" == "foo"

  true

ruby> "foo" == "bar"

  false  

注意:在Ruby 1.0里,以上结果以大写字母出现.

好,让我们来试试这些特性.下面是一个猜词的谜题,可能"谜题"这个词用在下面的东西上太酷了一点;-)

# save this as guess.rb

words = ['foobar', 'baz', 'quux']

secret = words[rand(3)]

print "guess? "

while guess = STDIN.gets  

   guess.chop!  

   if guess == secret

      print "You win!\n"    

      break  

   else   

      print "Sorry, you lose.\n"  

   end  

   print "guess? "

end

print "The word was ", secret, ".\n" 

现在,别太担心代码细节了.下面是谜题程序运行的一个对话.

% ruby guess.rb
guess? foobar
Sorry, you lose.
guess? quux
Sorry, you lose.
guess? ^D
The word was baz.