From Class to State+Functions

1-UserProfile.java

// Start from a class, that is state and behaviour together
class UserProfile {
    
    private String username;
    private String password;
    private Date lastLogIn;
    private boolean isLoggedIn;

    public UserProfile( String username,
                        String password,
                        Date lastLogin) {
        this.username = username;
        this.password = password;
        this.lastLogin = lastLogin;
        this.isLoggedIn = false;
    }

    public boolean tryLogin(String username, String password) {
        final boolean ok = this.username.equals(username) 
            && this.password.equals(password);
        if(ok) {
            this.isLoggedIn = true;
            this.lastLogin = new Date();
        }
    }

    public void logOut() {
        this.isLoggedIn = false;
    }

    public String getUsername() { return this.username; }
    public String getPassword() { return this.password; }
    public Date getLastLogin() { return this.latLogin; }
    public boolean isLoggedIn() { return this.isLoggedIn; }

    public static void main(...) {
        // snip...
        final UserProfile requestedProfile = new UserProfile(usernameFromDb, passwordFromDb, lastPersistedLogin);
        final boolean success = requestedProfile.tryLogin(providedUsername, providedPassword);
        if(success) {
            // do something
        } else {
            // or something else
        }
    }
}

2-UserProfile.py

# make 'this' (or self, in py) explicit (getters left for demonstrative purpose)

class UserProfile:

    def __init__(self, username, password, lastLogin):
        self.username = username;
        self.password = password;
        self.lastLogin = lastLogin;
        self.isLoggedIn = false;

    def tryLogin(self, username, password) {
        ok = self.username == username and self._password == password
        if ok:
            self.isLoggedIn = True
            self.lastLogin = datetime.now()

    def logOut(self):
        self.isLoggedIn = False;


    def getUsername(self):
        self.username

    def getPassword(self):
        self.password

    def getLastLogin(self):
        self.lastLogin

    def isLoggedIn(self):
        self.isLoggedIn


# snip...
requestedProfile = UserProfile(usernameFromDb, passwordFromDb, lastPersistedLogin)
success = requestedProfile.tryLogin(providedUsername, providedPassword)
if success:
    # do something
else:
    # or something else

3-user_profile.erl

%% drop class and make it a namespace instead 
%% (keep login history instead of only last one
%% to show how encapsulation of a representation is still useful)

-module(user_profile).
-export([new/3]).
-export([try_login/3]).
-export([logout/1]).
-export([username/1]).
-export([password/1]).
-export([last_login/1]).
-export([is_logged_in/1]).

new(Username, Password, LastLogin) ->
    {Username, {plain, Password}, [LastLogin], false}.

try_login(LoginUsername, LoginPassword, UserInfo) ->
    {Username, {plain, Password}, Logins, _Logged} = UserInfo,
    if
        Username =:= LoginUsername andalso Password =:= LoginPassword -> {ok, {Username, {plain, Password}, [now() | Logins], true}};
        true -> error
    end.

log_out(UserInfo) ->
    {Username, {Encryption, Password}, Logins, _Logged} = UserInfo,
    {Username, {Encryption, Password}, Logins, false}.

get_username(UserInfo) ->
    {Username, _EncryptionAndPassword, _Logins, _Logged} = UserInfo,
    Username.

get_password(UserInfo) ->
    {_Username, {plain, Password}, _Logins, _Logged} = UserInfo,
    Password.

get_last_login(UserInfo) ->
    {_Username, _EncryptionAndPassword, [LastLogin | OtherLogins], _Logged} = UserInfo,
    LastLogin.

is_logged_in(UserInfo) ->
    {Username, _EncryptionAndPassword, _Logins, Logged} = UserInfo,
    Logged.




main(...) ->
    % snip...

    UserProfile = user_profile:new(UsernameFromDb, PasswordFromDb, LastPersistedLogin),
    Success = User_profile:tryLogin(ProvidedUsername, ProvidedPassword, UserProfile),
    case Success of
        {ok, LoggedUserProfile} ->
            % do something
            ;
        error ->
            % or something else
    end.

4-user_profile.erl

%% use language feature awesomeness

-module(user_profile).
-export([new/3]).
-export([try_login/3]).
-export([logout/1]).
-export([username/1]).
-export([password/1]).
-export([last_login/1]).
-export([is_logged_in/1]).

new(Username, Password, LastLogin) ->
    {Username, {plain, Password}, [LastLogin], false}.

try_login(Username, Password, {Username, {plain, Password}, Logins, _Logged}) ->
    {ok, {Username, {plain, Password}, [now() | Logins], true}};
try_login(Username, Password, UserInfo) ->
    error.

log_out({Username, {plain, Password}, Logins, _Logged}) ->
    {Username, {plain, Password}, Logins, false}.

get_username({Username, _, _, _}) ->
    Username.

get_password({_, {plain, Password}, _, _}) ->
    Password.

get_last_login({_, _, [ LastLogin | _OtherLogins], _}) ->
    LastLogin.

is_logged_in({_, _, _, IsLogged}) ->
    IsLogged.