字符串分解为数组

procedure TForm1.btn1Click(Sender: TObject);
var
 MultiDB:array[0..20] of string;
 multiname:string;
 i,j,z:Integer;
begin
    multiname:='a,bc,def,ghth,';
   j:=1;
   z:=0;
   for I := 1 to Length(multiname) do
   begin
      if Copy(MulTiName,i,1)=','then
      begin
        MultiDB[z]:=Copy(MulTiName,j,i-j);
        j:=i;
        z:=z+1;
      end;

    
   end;
   ShowMessage('d');
end;