ruby字符串学习笔记4

1 单独处理字符串的字符

如果处理的是ASCII码的文档使用string#each_byte

注意 没有 string#each方法，String#each_byte 速度比 String#scan快 ，String#scan用于配合正则表达式时使用

'foobar'.each_byte { |x| puts "#{x} = #{x.chr}" }
# 102 = f
# 111 = o
# 111 = o
# 98 = b
# 97 = a
# 114 = r

'foobar'.scan( /./ ) { |c| puts c }
# f
# o
# o
# b
# a
# r

2 分割一段文本。并对每个单词进行处理

class String
  def word_count
    frequencies = Hash.new(0)
    downcase.scan(/\w+/) { |word| frequencies[word] += 1 }
     frequencies
  end
end
p %{Dogs dogs dog dog dogs.}.word_count

3 字符串大小写转换

s = 'HELLO, I am not here , I WENT to tHe MaRKEt'

p s.upcase # "HELLO, I AM NOT HERE , I WENT TO THE MARKET"
p s.downcase # "hello, i am not here , i went to the market"
p s.swapcase # "hello, i AM NOT HERE , i went TO ThE mArkeT"
p s.capitalize # "Hello, i am not here , i went to the market"

s = "abc"

p s.tr('a','A')

4处理空白字符

移除开头和结尾空白字符

" \tWhitespace at beginning and end. \t\n\n".strip
# => "Whitespace at beginning and end."

移除一端的空格

s = "
Whitespace madness! "
s.lstrip
# => "Whitespace madness! "
s.rstrip
# => "
Whitespace madness!"

5 判断一个对象可否作为字符串

判断对象是否有to_str方法

'A string'.respond_to? :to_str # => true
Exception.new.respond_to? :to_str # => true
4.respond_to? :to_str # => false