Ruby Hash

Posted by On 5月 14, 2014 0 Comment

Contents

  • Hash
  • Hash key-value

Hash

Create hash {}, key => value

a = {"foo1" => 1, "foo2" => 2, "foo3" => 3}
a["foo1"]   # 1
a["foo2"] = 20
p a

Hash[]

Hash["apple", "fruit", "coffee", "drink"]
#=> {"apple"=>"fruit", "coffee"=>"drink"}

Default value

a = Hash.new(5)
a[:foo1]    #=> 5

Not existed

nil

a = {}
a[:rena]    # nil

Use symbol as key

a = {:rena => 1, :jurina => 2, :manatsu => 3}

Hash key-value

[], keys, values, values_at, fetch, select

Name Description
[]= Change
delete Delete element(return deleted item)
reject Delete item of which block is true
delete_if Same above(break)
replace Replace hash
shift Remove key and value(1 set randomly) and return array
merge Merge hash and return it
update Integrate hash
invert Return hash which value and key are reversed
clear Clear data

Examples

a = {"apple" => "iOS", "google" => "Android"}
a["apple"] = "red"
a["orange"] = "orange"
a.delete("google")
a = {"mayuyu" => "watanabe", "rena" => "matsui"}
a.reject{|key, value| value == "matsui"}
 
a.replace({"paruru" => "shimazaki", "kojiharu" => "kojima"})

shift method pick up randomly

Search Hash

ength, size, empty?, has_key?, include?, key?, member?, has_value, value?
length, size, empty?

a = {"apple" => "fruit", "coffee" => "drink"}
a.size      #=> 2
a.empty?    #=> false

has_key?, include?, key?, member? : Check key existence

a = {"apple" => "iOS", "google" => "android"}
a.value?("iOS") #=> true
a.key?("microsoft") #=> false

Hath to Array

to_a

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