字符串处理函数
1.返回字符串的长度

str.length => integer

2.判断字符串中是否包含另一个串

str.include? other_str => true or false
"hello".include? "lo" #=> true
"hello".include? "ol" #=> false
"hello".include? ?h #=> true

3.字符串插入:

str.insert(index, other_str) => str
"abcd".insert(0, 'X') #=> "Xabcd"
"abcd".insert(3, 'X') #=> "abcXd"
"abcd".insert(4, 'X') #=> "abcdX"
"abcd".insert(-3, 'X') #=> "abXcd"
"abcd".insert(-1, 'X') #=> "abcdX"

4.字符串分隔,默认分隔符为空格

str.split(pattern=$;, [limit]) => anArray
" now's the time".split #=> ["now's", "the", "time"]
"1, 2.34,56, 7".split(%r{,\s}) #=> ["1", "2.34", "56", "7"]
"hello".split(//) #=> ["h", "e", "l", "l", "o"]
"hello".split(//, 3) #=> ["h", "e", "llo"]
"hi mom".split(%r{\s}) #=> ["h", "i", "m", "o", "m"]
"mellow yellow".split("ello") #=> ["m", "w y", "w"]
"1,2,,3,4,,".split(',') #=> ["1", "2", "", "3", "4"]
"1,2,,3,4,,".split(',', 4) #=> ["1", "2", "", "3,4,,"]

5.字符串替换

str.gsub(pattern, replacement) => new_str
str.gsub(pattern) {|match| block } => new_str
"hello".gsub(/[aeiou]/, '') #=> "hll" #将元音替换成号
"hello".gsub(/([aeiou])/, '<\1>') #=> "h<e>ll<o>" #将元音加上尖括号,\1表示保留原有字符???
"hello".gsub(/./) {|s| s[0].to_s + ' '} #=> "104 101 108 108 111 "

字符串替换二:

str.replace(other_str) => str
s = "hello" #=> "hello"
s.replace "world" #=> "world"

6.字符串删除:

str.delete([other_str]+) => new_str
"hello".delete "l","lo" #=> "heo"
"hello".delete "lo" #=> "he"
"hello".delete "aeiou", "^e" #=> "hell"
"hello".delete "ej-m" #=> "ho"

7.去掉前和后的空格

str.lstrip => new_str
" hello ".lstrip #=> "hello "
"hello".lstrip #=> "hello"

8.字符串匹配

str.match(pattern) => matchdata or nil

9.字符串反转

str.reverse => new_str
"stressed".reverse #=> "desserts"

10.去掉重复的字符

str.squeeze([other_str]*) => new_str
"yellow moon".squeeze #=> "yelow mon" #默认去掉串中所有重复的字符
" now is the".squeeze(" ") #=> " now is the" #去掉串中重复的空格
"putters shoot balls".squeeze("m-z") #=> "puters shot balls" #去掉指定范围内的重复字符

11.转化成数字

str.to_i=> str
"12345".to_i #=> 12345

chomp和chop的区别:
chomp:去掉字符串末尾的\n或\r
chop:去掉字符串末尾的最后一个字符,不管是\n\r还是普通字符

"hello".chomp #=> "hello"
"hello\n".chomp #=> "hello"
"hello\r\n".chomp #=> "hello"
"hello\n\r".chomp #=> "hello\n"
"hello\r".chomp #=> "hello"
"hello".chomp("llo") #=> "he"

"string\r\n".chop #=> "string"
"string\n\r".chop #=> "string\n"
"string\n".chop #=> "string"
"string".chop #=> "strin"