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Ruby Hash

2024-07-29 02:19:34   222人阅读

创建一个Hash

names = Hash.newnames["chn"] = "LiuLei"names["eng"] = "Voctrals"names["jpn"] = "ryourayi"
names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}
#创建一个有默认值的hashnames3 = Hash.new("")p names3["any_thing"]　　#=> ""#创建一个没有默认值的hashnames4 = Hash.newp names4["any_thing"]    #=> nil
p names4 = Hash.newnames4.store("xi", "jinping")p names4.fetch("xi")    #=>jinpingp names4.fetch("liu")    #=>会抛异常p names4.fetch("liu", "voctrals")    #=>voctrals,第二个参数作为默认值返回

 

取出Hash对象的所有的键和值

names5 = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}p names5.keys    #=>["chn", "eng", "jpn"]p names5.values    #=>["Liulei", "Voctrals", "ryourayi"]

 

Hash转化为数组

names6 = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}p names6.to_a    #=>[["chn", "Liulei"], ["eng", "Voctrals"], ["jpn", "ryourayi"]]

 

each相关（不明白each_value有啥用！！！）

names6 = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}names6.each{|key, value|    print "when ", key, " values ", value, ".\n"}names6.each_key{|key|    print "when ", key, " values ", names6[key], ".\n"}

 

提供默认值

# method one
names = Hash.new(1)names.store("a", 97)p names["a"]    #=>97p names["b"]    #=>1#method two
names2 = Hash.new{|hash, key|    hash[key] = key}names2.store("a", 100)p names2["a"]    #=>100p names2["b"]    #=>"b"

#method three
names3 = {}

p names3.fetch("a", "voctrals")　　#=>"voctrals"

 

是否含有某个key

names2 = Hash.new{|hash, key|    hash[key] = key}names2.store("a", 100)p names2.key?("b")    #=>falsep names2.has_key?("b")    #=>falsep names2.include?("b")    #=>falsep names2.member?("b")    #=>false

 

是否含有某个value

names2 = Hash.new{|hash, key|    hash[key] = key}names2.store("a", 100)p names2.value?(100)    #=>truep names2.has_value?(100)    #=>truep names2.has_value?(200)    #=>false

 

查询Hash的大小，是否为空

names2 = Hash.new{|hash, key|    hash[key] = key}names2.store("a", 100)p names2.size    #=>1，与length相同p names2.empty?    #=>false

 

删除一个键值对

names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}p names.size    #=>3p names.delete("chn")    #=>"Liulei",返回值为删除掉的valuep names.length    #=>2
p names.delete("chn2"){|key| "NOT EXSIT #{key}"}　　#=>"NOT EXSIT chn2"，当不存在key的时候触发后面的代码块

 

条件删除

names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}p names.delete_if{|key| key=="jpn"}    #=>{"chn"=>"Liulei", "eng"=>"Voctrals"}p names    #=>{"chn"=>"Liulei", "eng"=>"Voctrals"}
names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}p names.delete_if{|key, value| key=="jpn" || value=http://www.mamicode.com/="Voctrals"}    #=>{"chn"=>"Liulei"}p names    #=>{"chn"=>"Liulei"}
names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}p names.reject!{|key, value| key=="jpnX" || value=http://www.mamicode.com/="VoctralsX"}        #=>nil，没有被删除时返回值为nil,而delete_if的返回值为原Hashp names        #=>{"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}

 

清空Hash，仅仅针对于调用clear的hash对象，和h = Hash.new效果是一样的

names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}p names.clear    #=>{}p names    #=>{}

 

取出文件中各个单词出现的次数

count = Hash.new(0)while line = gets    words = line.split    words.each{|word|        count[word] += 1    }endcount.sort{|a, b|    #sort，原理是count.to_a，获得数组，所有的数组再分配给a,b    #<=>当a[1]>b[1]返回正数，相等返回0，小于返回负数    a[1] <=> b[1]}.each{|key, value|    print key, " appears ", value, " times.", "\n"}

 

Ruby Hash


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