Title here
Summary here
Structs in Erlang
Go’s structs are typed collections of fields. They’re useful for grouping data together to form records.
This person struct type has name and age fields.
-module(structs).
-export([new_person/1, main/0]).
-record(person, {name, age = 0}).
new_person(Name) ->
#person{name=Name, age=42}.
main() ->
% This syntax creates a new struct
io:format("~p~n", [#person{name="Bob", age=20}]),
% You can name the fields when initializing a struct
io:format("~p~n", [#person{name="Alice", age=30}]),
% Omitted fields will be zero-valued
io:format("~p~n", [#person{name="Fred"}]),
% An & prefix yields a pointer to the struct
P1 = #person{name="Ann", age=40},
Ptr1 = erlang:make_ref(),
io:format("~p~n", [Ptr1]),
% It’s idiomatic to encapsulate new struct creation in constructor functions
io:format("~p~n", [new_person("Jon")]),
% Access struct fields with a dot
S = #person{name="Sean", age=50},
io:format("~p~n", [S#person.name]),
% You can also use dots with struct pointers - the pointers are automatically dereferenced
SP = &S,
io:format("~p~n", [SP#person.age]),
% Structs are mutable
NewSP = setelement(2, SP, 51),
io:format("~p~n", [NewSP#person.age]),
% If a struct type is only used for a single value, we don’t
% have to give it a name. The value can have an anonymous
% struct type.
Dog = #{name => "Rex", isGood => true},
io:format("~p~n", [Dog]).To run the program, compile it and then execute the main function.
$ erlc structs.erl
$ erl -noshell -s structs main -s init stop
#person{name = "Bob", age = 20}
#person{name = "Alice", age = 30}
#person{name = "Fred", age = 0}
#Ref<0.0.0.106>
#person{name = "Jon", age = 42}
"Sean"
50
51
#{isGood => true, name => "Rex"}Now that we can run and build basic Erlang programs, let’s learn more about the language.