几种常见Ruby on Rails内置方法介绍

Ruby on Rails内置方法之对象是否为空blank?

    puts [ ].blank? #=> true  
    puts { 1 => 2}.blank? #=> false  
    puts " cat ".blank? #=> false  
    puts "".blank? #=> true  
    puts " ".blank? #自动去除前后空格=> true  
    puts nil.blank? #=> true 

Ruby on Rails内置方法之排序：group_by()

groups = posts.group_by {|post| post.author_id}

Ruby on Rails内置方法之组句：to_sentence()

    puts [ "ant", "bat", "cat"].
    to_sentence #=> "ant, bat, and cat"  
    puts [ "ant", "bat", "cat"].
    to_sentence(:connector => 
    "and not forgetting")  
    #=> "ant, bat, and not forgetting cat"  
    puts [ "ant", "bat", "cat"].
    to_sentence(:skip_last_comma => true)  
    #=> "ant, bat and cat" 

Ruby on Rails内置方法之分组：in_groups_of()

    [1,2,3,4,5,6,7].in_groups_of(3) 
    {|slice| p slice}  
    #=> [1, 2, 3]  
    [4, 5, 6]  
    [7,nil, nil]  
    [1,2,3,4,5,6,7].in_groups
    _of(3,"X") {|slice| p slice}  
    #=> [1, 2, 3]  
    [4, 5, 6]  
    [7,"X", "X"] 

Ruby on Rails内置方法之字符串方法：

    string = "Now is the time" 
    puts string.at(2) #=> "w"  
    puts string.from(8) #=> "he time"  
    puts string.to(8) #=> "Now is th"  
    puts string.first #=> "N"  
    puts string.first(3) #=> "Now"  
    puts string.last #=> "e"  
    puts string.last(4) #=> "time"  
    puts string.starts_with?("No") #=> true  
    puts string.ends_with?("ME") #=> false  
     
    count = Hash.new(0)  
    string.each_char {|ch| count[ch] += 1}  
    p count #=> {" "=>3, "w"=>1, "m"=>1,
     "N"=>1, "o"=>1, "e"=>2, "h"=>1, 
    "s"=>1, "t"=>2, "i"=>2}