How to initialize the array

[Doe]

Hello, I am a beginner and I was trying to get a value from the string and put it into the array. An error message "Warning: Variable "code" of a managed type does not seem to be initialized". How do I solve it?

program pra2;
uses SysUtils;
var
  code:TStringArray;
  j,i:integer;
  text:string;

begin
  text:='rafrgqaf';
  code[0]:=text[1];
  writeln(code[0]);
  readln();
  end.           

[lucamar]

It's just a warning, in case you forgot to initialize the array (or other managed type, like String), and it can usually be either ignored or shut down by initializing it, for example with:

Code: Pascal  [Select][+][-]

1. code := Default(TStringArray);

Note, though, that in your case you did really forget to initialize the array, and that in a way that might lead you to an error/exception. Instead, do this:

Code: Pascal  [Select][+][-]

1. program pra2;
2. uses SysUtils;
3. var
4.   code:TStringArray;
5.   j,i:integer;
6.   text:string;
7.  
8. begin
9.   text:='rafrgqaf';
10.   { Initialize the array to contain 1 element }
11.   SetLength(code, 1);
12.   { you'll still get the warning: just ignore it,
13.     deactivate it or use Default() to pre-initialize }
14.   code[0]:=text[1];
15.   writeln(code[0]);
16.   readln();
17. end.

[Doe]

Got it, thanks a lot!

[furious programming]

You can also use a special array constructor:

Code: Pascal  [Select][+][-]

1. Code := TStringArray.Create('r', 'a', 'f');

for both literals and variables:

Code: Pascal  [Select][+][-]

1. var
2.   Code: TStringArray;
3.   Foo: String = 'abc';
4. begin
5.   Code := TStringArray.Create(Foo[1], Foo[2], Foo[3]);
6.  
7.   Write(Code[0], Code[1], Code[2]); // prints "abc"
8. end;

[lucamar]

You can also use a special array constructor [...]

Is that already available in 3.2.0? Man, I didn't know! I thought it was still Trunk-only

[furious programming]

It was available in the previous stable version of the FPC, so… yes — you can use it in 3.2.0.

[lucamar]

It was available in the previous stable version of the FPC, so… yes — you can use it in 3.2.0.

It seems I should re-read the docs more frequently:

As of version 3.0 of Free Pascal, Dynamic array types have a constructor. This is intrinsic, the compiler provides it. [...]

[Thaddy]

Or the simplest, on declaration (from 3.2.0):

Code: Pascal  [Select][+][-]

1. {$mode delphi}
2. var
3. a:array of integer = [1,2,3,4];
4. i:integer;
5. begin
6.  for i in a do writeln(i);
7. end.

And in objfpc mode:

Code: Pascal  [Select][+][-]

1. {$mode objfpc}
2. var
3. a:array of integer = (1,2,3,4);
4. i:integer;
5. begin
6.  for i in a do writeln(i);
7. end.

Note the different notation between the modes.

In your case this becomes something like this:

Code: Pascal  [Select][+][-]

1. {$mode objfpc}
2. var
3. a:array of AnsiChar = ('r', 'a', 'f');
4. c:AnsiChar;
5. begin
6.  for c in a do writeln(c);
7. end.

[JanRoza]

Thaddy, you show Delphi mode twice and no objfpc mode.
(old clipboard content maybe?). 

[Thaddy]

corrected. tnx

[PascalDragon]

Hello, I am a beginner and I was trying to get a value from the string and put it into the array. An error message "Warning: Variable "code" of a managed type does not seem to be initialized". How do I solve it?

program pra2;
uses SysUtils;
var
  code:TStringArray;
  j,i:integer;
  text:string;

begin
  text:='rafrgqaf';
  code[0]:=text[1];
  writeln(code[0]);
  readln();
  end.           

By default an array is empty, thus simply using code[0] would be an error. So you need to initialize its length using SetLength(code, xxx) where xxx is the length you want.

You can also use a special array constructor [...]

Is that already available in 3.2.0? Man, I didn't know! I thought it was still Trunk-only

Since 3.2.0 I'd suggest to use the inline array constructor [ ... ] instead of TSomeArrayType.Create, because the former does not require a named type.

[Thaddy]

Since 3.2.0 I'd suggest to use the inline array constructor [ ... ] instead of TSomeArrayType.Create, because the former does not require a named type.

Or, as I explained, depending on mode, with (..). Your suggestion covers Delphi syntax only.
But as explained above, I agree. It is all in my - corrected - example.
Nice work, btw, to implement this!

[PascalDragon]

Since 3.2.0 I'd suggest to use the inline array constructor [ ... ] instead of TSomeArrayType.Create, because the former does not require a named type.

Or, as I explained, depending on mode, with (..). Your suggestion covers Delphi syntax only.
But as explained above, I agree. It is all in my - corrected - example.
Nice work, btw, to implement this!

I meant inline in code, not constant. For code it's always the [ ... ] syntax.

[lucamar]

My guess (and it's just that: a guess*) is that the OP's code is just an example and he will need to "transform" arbitrary strings with content unknown at compile time, so using a constructor won't be possible.

But it's good to know that it's already implemented, whether as a explicit Create or as an implicit simple assignment. And it's also good to know the implicit constructor was implemented for 3.2 ... I knew there was some thing about it which I wasn't sure whether it was already there or waiting in trunk

*Fact is I can't imagine how (except in very special circumstances) it would be useful to move a string char by char to an array when one can easily access it that way by itself, but I suppose there must be some reason: otherwise the OP's question would make no sense

[simone]

Just for curiosity: why this syntax difference between Delphi and ObjFPC modes?