5、字符串 - RUBY文档中心

5、字符串

转帖：oasis_me　　发表时间：2005-6-15 4:03:57　　点击次数：530

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字符由一个前置的斜杠引出,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.

(考虑到1/3的成功率,也许我本该做得好一点.)