字典
散列表和散列字典都實現了Dict的行為。Keyword模塊也基本實現了，不同之處在于它支持重復鍵。
Eunm.into可以將一種類型的收集映射轉化成另一種。
defmodule Sum dodef values(dict) dodict |> Dict.values |> Enum.sumend endhd = [ one: 1, two: 2, three: 3 ] |> Enum.into HashDict.new IO.puts Sum.values(hd) #=>6
Dict相關API
kw_list = [name: "Dave", likes: "Programming", where: "Dallas"] hashdict = Enum.into kw_list, HashDixt.new map = Enum.into kw_list, Map.newkw_list[:name] #=>"Dave" hashdict[:likes] #=>"Programming" map[:where] #=>"Dallas"hashdict = Dict.drop(hashdict, [:where, :likes]) #=>HashDict<[name: "Dave"]> hashdict = Dict.put(hashdict, :also_likes, "Ruby) #=>HashDict<[name: "Dave", also_likes: "Ruby"]> combo = Dict.merge(map, hashdict) #合并=>%{also_likes: "Ruby", likes: "Programming", name: "Dave", where: "Dallas"}
例子：
people = [%{ name: "Grumpy, height: 1.24 },%{ name: "Dave", height: 1.88 },%{ name: "Dopey", height: 1.32 },%{ name: "Shaquille", height: 2.16 },%{ name: "Sneezy", height: 1.28 }] for person = %{ height: height } <- people, #將列表中的散列表綁定到person ，并將高度值綁定到heightheight > 1.5, #篩選出高度高于1.5的do: IO.inspect person
例子2：
def book(%{name: name, height: height}) when height > 1.9 do... enddef book(%{name: name, height: height}) when height < 1.3 do... enddef book(person) do... endpeople |> Enum.each(&HotelRoom.book/1)
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更新散列表
new_map = %{ old_map | key => value, ...}，會創建一個新的散列表，它是舊散列表的拷貝，但是管道運算符右邊與鍵所對應的值會被更新。
m = %{ a: 1, b: 2, c: 3 }
m1 = %{ m | b: "two", c: "three" } #%{ a: 1, b: "two, c: "three" }#要增加新的鍵值需要使用Dict.put_new/3函數 ?
結構體
結構體就是模塊，它封裝了一個有限形式的散列表。有限是因為鍵必須為原子，并且這些散列表不具備Dict和Access特性。使用defstruct來定義散列表的性質。
結構體的使用就相當于是散列表一樣，只不過結構體有默認參數。
defmodule Subscriber dodefstruct name: "", paid: false, over_18: true ends1 = %Subscriber{} #=>%Subscriber{name: "", over_18: true, paid: false } s2 = %Subscriber{name: "Mary", paid: true} #=>%Subscriber{name: "Mary", over_18: true, paid: true }匹配 s2.name #通過點標記訪問，鍵必須為原子，符合結構體的特性 %Subscriber{name: a_name} = s3 a_name #=>"Mary"
更新
s3 = %Subscriber{ s2 | name: "Marie" }
例子：
defmodule Attendee dodefstruct name: "", paid: false, over_18: truedef may_attend_after_party(attendee = %Attendee{}) do #函數參數使用 %Attendee{} 接受結構體attendee.paid && attendee.over_18enddef print_vip_badge(%Attendee{name: name}) when name != "" doIO.puts "Very cheap badge for #{name}"enddef print_vip_bage(%Attendee{}) foraise "missing name for badge"end end
散列表實現了Access協議，所以可以使用 [] 訪問。我們可以給結構體添加這個功能。
defmodule Attendee do@derive Accessdefstruct name: "", over_18: false enda = %Attendee{name: "Sally", over_18: true} a[:name] #=> "Sally
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嵌套字典結構
字典類型可以讓鍵和值相關聯，這些值本身也可以是字典類型。
defmodule Customer dodefstruct name: "", company: "" enddefmodule BugReport dodefstruct owner: %{}, details: "", serverity: 1 endreport = %BugReport{owner: %Customer{name: "Dave", company: "Pragmatic"}, detail: "broken"}#訪問 report.owner.company#更新/修改 report = %BugReport{ report | owner: %Customer{ report.owner | company: "PragProg" }}#put_in可以設置嵌套結構里面的值 put_in(report.owner.company, "PargProg")#update_in可以讓我們在結構體上的某一個值上執行一個函數 update_in(report.owner.name, &("Mr. " <> &1)) #連接 "Mr. "和name
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