Ruby Hash

names = Hash.new
names["chn"] = "LiuLei"
names["eng"] = "Voctrals"
names["jpn"] = "ryourayi"

names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}

#创建一个有默认值的hash
names3 = Hash.new("")
p names3["any_thing"]　　#=> ""
#创建一个没有默认值的hash
names4 = Hash.new
p names4["any_thing"]    #=> nil

p names4 = Hash.new
names4.store("xi", "jinping")
p names4.fetch("xi")    #=>jinping
p 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

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

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

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"
}

# method one
names = Hash.new(1)
names.store("a", 97)

p names["a"]    #=>97
p names["b"]    #=>1

#method two
names2 = Hash.new{|hash, key|
    hash[key] = key
}
names2.store("a", 100)

p names2["a"]    #=>100
p names2["b"]    #=>"b"

#method three
names3 = {}

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

names2 = Hash.new{|hash, key|
    hash[key] = key
}
names2.store("a", 100)

p names2.key?("b")    #=>false
p names2.has_key?("b")    #=>false
p names2.include?("b")    #=>false
p names2.member?("b")    #=>false

names2 = Hash.new{|hash, key|
    hash[key] = key
}
names2.store("a", 100)

p names2.value?(100)    #=>true
p names2.has_value?(100)    #=>true
p names2.has_value?(200)    #=>false

names2 = Hash.new{|hash, key|
    hash[key] = key
}
names2.store("a", 100)

p names2.size    #=>1，与length相同
p names2.empty?    #=>false

names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}

p names.size    #=>3
p names.delete("chn")    #=>"Liulei",返回值为删除掉的value
p 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

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=="Voctrals"}    #=>{"chn"=>"Liulei"}
p names    #=>{"chn"=>"Liulei"}

names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}

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

names = {"chn" => "Liulei", "eng" => "Voctrals", "jpn" =>"ryourayi"}

p names.clear    #=>{}
p names    #=>{}

count = Hash.new(0)

while line = gets
    words = line.split
    words.each{|word|
        count[word] += 1
    }
end


count.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"
}