Help - incompatible type error.
lazarus / 16-Databases

----------------------------------------------------------------------
Muggy · 2015-02-22 22:07

I am trying to get a simple username and password program to work, it
checks the username is correct and then checks if the password is
correct afterwards. The username and password are stored in an SQL
database. I have yet to add in password checking as that is the same
as username checking but username checking is not working. Here is all
the relevent code

  var
  UsernameEnt, //stores the username and password the user entered
  PasswordEnt,
  UsernameCur, //stores the current username and password being
checked in the database
  PasswordCur,
  hold //for holding the current query in the form of text
  :String;
  IDCur
  :Integer=0; //stores the current id
begin
  UsernameEnt:=Username.text;
  PasswordEnt:=Password.text;
  while not adminform.adminquery.Eof do
  begin
    IDCur:=IDCur+1;
    hold:='SELECT User FROM loginInf WHERE PKey='+IntToStr(IDCur)+';';
    adminform.adminquery.Active:=true;
    if (adminform.adminquery.SQL.text:=hold)=UsernameEnt then
     //login succesful
     Indicatortext.caption:='Welcome!';
     IndicatorColour.Color:=$00FF00;
     Application.createform(TAdminform,AdminForm);
     LogInForm.hide;
     Adminform.showmodal;
     else
  end;
  //login unsuccesful
  Indicatortext.caption:='nah!';
  IndicatorColour.Color:=$0000FF;

And the error I get is
adminsignin.pas(57,8) Error: Incompatible types: got "untyped"
expected "AnsiString"
where line 57 is  if (adminform.adminquery.SQL.text:=hold)=UsernameEnt
then

Please help and ask for further clarification if this is at all
unclear.

Sorry i am new here, sorry if this is in the wrong subforum.

----------------------------------------------------------------------
Leledumbo · 2015-02-22 23:56

Assignment is a statement, not an expression, it has no value.

----------------------------------------------------------------------
Muggy · 2015-02-23 00:09

I am afraid i dont know what that means, could you explain in more
detail. Perhaps hint at how i would fix this.

----------------------------------------------------------------------
engkin · 2015-02-23 01:08

What are you trying to do in line 57?

----------------------------------------------------------------------
Leledumbo · 2015-02-23 05:47

Quote from: Muggy on February 23, 2015, 01:09:46 amI am afraid i dont
know what that means, could you explain in more detail. Perhaps hint
at how i would fix this.
Then google it. Hint to fix: you can't compare something that has no
type (statement) with something else that has a type (expression).

----------------------------------------------------------------------
Muggy · 2015-02-23 08:20

Quote from: engkin on February 23, 2015, 02:08:44 amWhat are you
trying to do in line 57?

I am trying to check if the username at a specific primary key which
is stepped matches the username the user has entered, and if it does
then it will run the for loop.

----------------------------------------------------------------------
engkin · 2015-02-23 08:31

Quote from: Muggy on February 23, 2015, 09:20:02 amQuote from: engkin
on February 23, 2015, 02:08:44 amWhat are you trying to do in line 57?

I am trying to check if the username at a specific primary key which
is stepped matches the username the user has entered, and if it does
then it will run the for loop.

I don't think this is the right way to use Pascal or SQL.

----------------------------------------------------------------------
mangakissa · 2015-02-23 08:52

First of all, this is more readdable:
Code: [Select]var Username  :String;
    Password  :String;
begin
  Username :=Username.text;
  Password :=Password.text;
  if locate('username;password',vararrayof([Username,Username]),[])
then
    showmessage('Welcome!')
  else
    showmessage('Incorrect');
end;
Never let you loginscreen the mainform. Let the mainform startup your
loginprocedure.
Code: [Select]//--mainform

procedure TMainform.onShow(senter : TObject);
var LoginForm : TLoginForm
begin
  LoginForm := TLoginForm.create(nil);
  try
    LoginForm.showmodal;
    if LoginForm.loggedin then
      showmessage('Welkome')
  finally
    LoginForm.free;
  end; 
end;

//loginform

type TLoginform : class(TForm);
......
public
  loggedin : boolean;
  ......
end;

procedure TLoginform.OnCreate(sender : tobject);
begin
  loggedin := false;
end

procedure TLoginform.OnButton1Click(sender : tobject);
var MyQuery : TQuery;
begin
  MyQuery := TQuery.create(nil);
  try
     MyQuery.connection := MyConnection;
     MyQuery.SQL.Text := 'SELECT count(username) AS sum_of_rows FROM
users WHERE username = :par1 AND password : par2';
     MyQuery.Params[0].AsString := EUserName.text;
     MyQuery.Params[1].AsString := EPassword.text;
     MyQuery.active := true;
     if MyQuery.fieldbyname('sum_of_rows').AsInteger = 1 then
     begin
       loggedin := true;
     end else
       showmessage('Wrong username or password');
    finally
    MyQuery.free;
  end;
end

This is only an example. If you're using SQLdb, don't forget
transactions.
The best thing is put your idea on paper. work it out with a PSD
Then create logical code on your program.

Is this your first time?