Erlang by Example: Maps

Maps

Maps are a type of data structures
also known as dictionaries or associative arrays.









To read the value associated with a given key
use the `maps:get/2` function.


Trying to get a non existing key will trow an
exception. A solution is to provide a default value.


To prevent exceptions in case a key is not found
you can use `maps:find/2`.









For more information about the `maps` module,
please consult the official docs

-module(map).
-compile([export_all]).

write(String, Value) ->
    io:format("~p = ~p~n", [String, Value]).

run() ->
    M1 = #{name => "Joe Doe", age => 25},
    write("Map", M1),


    write("Name", maps:get(name, M1)),



    write("Degree", maps:get(degree, M1, defaultdegree)),



    Keyname = randomkey,
    case maps:find(Keyname, M1) of
        {ok, Value} ->
            write("Found value", Value);
        error ->
            write("No value found for key", Keyname)
    end,
    ok.

1> c(map).
{ok,map}

2> map:run().
"Map" = #{age => 25,name => "Joe Doe"}
"Name" = "Joe Doe"
"Degree" = defaultdegree
"No value found for key" = randomkey
ok
50>

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