Ruby字符串處理函數
1.返回字符串的長度
str.length => integer 2.判斷字符串中是否包含另一個串
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,默認分隔符爲空格
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,,"] 也可以指定切分符：
"apples, pears, and peaches".split(", ") # ["apples", "pears", "and peaches"]
"lions and tigers and bears".split(/ and /) # ["lions", "tigers", "bears"]splite方法的第二個參數用來限制切分的返回結果個數，具體效果規則如下：
1.如果省略這個參數,則切分結果中末尾爲null的結果將被壓縮掉
2.如果是正數，則結果按照指定的限制數量進行切分，尾部的null結果也將會保留做爲結果
3.如果是負數，則切分結果數量無限制，並且保留尾部的null結果。
例如：
str = "alpha,beta,gamma,,"
list1 = str.split(",") # ["alpha","beta","gamma"]
list2 = str.split(",",2) # ["alpha", "beta,gamma,,"]
list3 = str.split(",",4) # ["alpha", "beta", "gamma", ","]
list4 = str.split(",",8) # ["alpha", "beta", "gamma", "", ""]
list5 = str.split(",",-1) # ["alpha", "beta", "gamma", "", ""]5、格式化字符串
Ruby的字符串格式話沿用了C的格式，在C中可用於sprintf或printf的格式話字符在Ruby中同樣適用：
name = "Bob"
age = 28
str = sprintf("Hi, %s... I see you're %d years old.", name, age)String類有個%方法，可以方面的做格式化的工作，它接受任何類型的單個值或一個數組：
str = "%-20s %3d" % [name,age]上面這個和下面這個式子是等效的
str = sprintf("%-20s %3d", name, age)我們還可以使用ljust,rjust,center方法來格式化我們的字符串：
str = "Moby-Dick"
s1 = str.ljust(13) #"Moby-Dick "
s2 = str.center(13) #" Moby-Dick "
s3 = str.rjust(13) #" Moby-Dick"6、控制字符串的大小寫
Ruby的String類提供了一組豐富的方法來控制大小寫：
s = "Hello,World"
s1 = s.downcase #"hello,world"
s2 = s.upcase #"HELLO,WORLD"capitalize方法把字符串第一個字符變大寫，其餘都是小寫：
s3 = s.capitalize #"Hello,world"swapcase則是把字符串中的每個字符的大小寫轉換一下(原來大寫的都小寫，反之亦然)：
s = "HELLO,world"
s1 = s.swapcase #"hello,WORLD"這些方法都有相應的in-place方法
(upcase!,downcase!,capitalize!,swapcase!)雖然，Ruby沒有提供內置的判斷字符是否是大小寫的方法，但是，這不是問題，我們可以通過正則表達式來完成這一點:
if string =~ /[a-z]/
puts "string contains lowercase charcters"
end
if string =~ /[A-Z]/
puts "string contains uppercase charcters"
end
if string =~ /[A-Z]/ and string =~ /a-z/
puts "string contains mixed case"
end
if string[0..0] =~ /[A-Z]/
puts "string starts with a capital letter"
end字符串的子串
Ruby提供了多種訪問操作字符串子串的方式，我們可以來看一下：
1.如果給出一組數字，則第一個數字代表取字符串的偏移位置，第二個數字表示
取的長度：
str = "Humpty Dumpty"
sub1 = str[7,4] # "Dump"
sub2 = str[7,99] # "Dumpty" (超過的長度按實際長度來取)
sub3 = str[10,-4] # nil (長度爲負數了)記住，上面的形式，很多從別的語言轉過來的ruby初學者會認爲給出的兩個數字是子串的開始和結束位置的偏移，這是錯誤的，務必記住。
給出的偏移是負數也是可以的,這樣，位置將從字符串末尾開始計算：
str1 = "Alice"
sub1 = str1[-3,3] # "ice"
str2 = "Through the Looking-Glass"
sub3 = str2[-13,4] # "Look"我們也可以給出一個Range來取子串：
str = "Winston Churchill"
sub1 = str[8..13] # "Church"
sub2 = str[-4..-1] # "hill"
sub3 = str[-1..-4] # nil
sub4 = str[25..30] # nil強大的是，正則表達式在這個時候也充分發揮着作用：
str = "Alistair Cooke"
sub1 = str[/l..t/] # "list"
sub2 = str[/s.*r/] # "stair"
sub3 = str[/foo/] # nil如果給出的是一個字符串，則如果目標字符串中含有這個給出的字符串，則返回這個給出的字符串，否則返回nil：
str = "theater"
sub1 = str["heat"] # "heat"
sub2 = str["eat"] # "eat"
sub3 = str["ate"] # "ate"
sub4 = str["beat"] # nil
sub5 = str["cheat"] # nil如果給出的是一個數字，則返回的是該數字對應索引處字符的ASCII碼：
str = "Aaron Burr"
ch1 = str[0] # 65
ch1 = str[1] # 97
ch3 = str[99] # nil同樣，我們不僅可以通過上面的方式訪問子串，還可以來向字符串設置內容：
str1 = "Humpty Dumpty"
str1[7,4] = "Moriar" # "Humpty Moriarty"
str2 = "Alice"
str2[-3,3] = "exandra" # "Alexandra"
str3 = "Through the Looking-Glass"
str3[-13,13] = "Mirror" # "Through the Mirror"
str4 = "Winston Churchill"
str4[8..13] = "H" # "Winston Hill"
str5 = "Alistair Cooke"
str5[/e$/] ="ie Monster" # "Alistair Cookie Monster"
str6 = "theater"
str6["er"] = "re" # "theatre"
str7 = "Aaron Burr"
str7[0] = 66 # "Baron Burr"