Ruby字符串处理

ruby字符串处理方法

截取

单个字符

>> s = "hello"
=> "hello"
>> s[0]  # 第一个字符
=> "h"
>> s[s.length - 1] # 左边数字符串长度减1个，即最后一个字符，左边数下标从0开始
=> "o"
>> s[-1]  # 右边数第一个字符
=> "o"
>> s[-s.length]   # 右边数字符串长度个，即第一个字符
=> "h"
>> s[10]  # 索引超出范围
=> nil

子串

>> s = "hello"
=> "hello"
>> s[2..3]    # 位于索引2到3的字符
=> "ll"
>> s[-3..-1] # 可以使用负的索引值，代表从右向左
=> "llo"
>> s[0..0]    # 第一个字符
=> "h"
>> s[0..1]    # 前两个字符
=> "he"
>> s[2..1]    # 起始索引大于结束索引，为空字符串
=> ""
>> s[7..10]  # 索引超出范围
=> nil

替换

替换单个

>> s = "hello"
=> "hello"
>> s[0] = "H"  # 将第一个字符替换为新字符
=> "H"
>> s
=> "Hello"
>> s[-2] = "L" # 将右边数第2个字符替换为新字符
=> "L"
>> s
=> "HelLo"
>> s[-1] = "UU" # 将右边数第1个字符替换为新字符集
=> "UU"
>> s
=> "HelLUU"
>> s[10] = "U"  # 抛出异常，索引超出范围
IndexError: index 10 out of string

替换子集

>> s = "hello"
=> "hello"
>> s[-2..-1] = "pas"  # 将从右数第2到第1个字符替换为新值
=> "pas"
>> s
=> "helpas"
>> s[0..0] = "please "  # 将第一个字符替换为新值
=> "please "
>> s
=> "please elpas"
>> s[6..10] = ""  # 将第6到10个字符替换为空值，即删除子串
=> ""
irb(main):029:0> s
=> "pleases"

包含

>> s = "hello"
=> "hello"
>> s["el"]  # 测试是否包含子串，包含的情况
=> "el"
>> s["LL"]  # 不包含的情况
=> nil
>> while(s["l"])   # 循环测试，将匹配到的所有子串替换为新值
>> s["l"]="L"
>> end
=> nil
>> s
=> "heLLo"