digitalmars.D.learn - Access vialotion

TheDGuy (18/18) Jun 22 2016 I have an array of buttons:

TheDGuy (5/23) Jun 22 2016 Okay, i solved it, instead of:

Moro Greenhand (3/28) Jun 22 2016 I would expect DMD to output a warning here, because of the

Steven Schveighoffer (7/37) Jun 23 2016 Variable shadowing only is reported by the compiler for function locals....

vladdeSV (11/36) Jun 22 2016 I would also suggest you use a foreach loop to iterate over the

Bell Baggins (3/41) Jun 22 2016 No, ref for classes is pointless. The ptr destination is always

TheDGuy <a.b gmail.de> writes:

I have an array of buttons:

class Window : MainWindow{
     private Button[4] bArr;
     this(){
         Button btn_1 = new Button();
         Button btn_2 = new Button();
         Button btn_3 = new Button();
         Button btn_4 = new Button();
         Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];
     }
     private void letButtonsFlash(){
         for(int i = 0; i < 4; i++){
             writeln(this.bArr[i].getName());
         }
     }
}

i don't understand why i get an 'Access Violation' - Error in the 
'for'-loop?

Jun 22 2016

TheDGuy <a.b gmail.de> writes:

On Wednesday, 22 June 2016 at 12:45:29 UTC, TheDGuy wrote:
 I have an array of buttons:

 class Window : MainWindow{
     private Button[4] bArr;
     this(){
         Button btn_1 = new Button();
         Button btn_2 = new Button();
         Button btn_3 = new Button();
         Button btn_4 = new Button();
         Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];
     }
     private void letButtonsFlash(){
         for(int i = 0; i < 4; i++){
             writeln(this.bArr[i].getName());
         }
     }
 }

 i don't understand why i get an 'Access Violation' - Error in 
 the 'for'-loop?

Okay, i solved it, instead of:
Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];

this:
bArr = [btn_1,btn_2,btn_3,btn_4];

Jun 22 2016

Moro Greenhand <MoroGreenhand gdfr.hu> writes:

On Wednesday, 22 June 2016 at 12:47:31 UTC, TheDGuy wrote:
 On Wednesday, 22 June 2016 at 12:45:29 UTC, TheDGuy wrote:
 I have an array of buttons:

 class Window : MainWindow{
     private Button[4] bArr;
     this(){
         Button btn_1 = new Button();
         Button btn_2 = new Button();
         Button btn_3 = new Button();
         Button btn_4 = new Button();
         Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];
     }
     private void letButtonsFlash(){
         for(int i = 0; i < 4; i++){
             writeln(this.bArr[i].getName());
         }
     }
 }

 i don't understand why i get an 'Access Violation' - Error in 
 the 'for'-loop?

 Okay, i solved it, instead of:
 Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];

 this:
 bArr = [btn_1,btn_2,btn_3,btn_4];

I would expect DMD to output a warning here, because of the 
shadowing...but after 3 verifications, nothing. Dscanner does.

Jun 22 2016

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 6/22/16 9:00 AM, Moro Greenhand wrote:
 On Wednesday, 22 June 2016 at 12:47:31 UTC, TheDGuy wrote:
 On Wednesday, 22 June 2016 at 12:45:29 UTC, TheDGuy wrote:
 I have an array of buttons:

 class Window : MainWindow{
     private Button[4] bArr;
     this(){
         Button btn_1 = new Button();
         Button btn_2 = new Button();
         Button btn_3 = new Button();
         Button btn_4 = new Button();
         Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];
     }
     private void letButtonsFlash(){
         for(int i = 0; i < 4; i++){
             writeln(this.bArr[i].getName());
         }
     }
 }

 i don't understand why i get an 'Access Violation' - Error in the
 'for'-loop?

 Okay, i solved it, instead of:
 Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];

 this:
 bArr = [btn_1,btn_2,btn_3,btn_4];

 I would expect DMD to output a warning here, because of the
 shadowing...but after 3 verifications, nothing. Dscanner does.

Variable shadowing only is reported by the compiler for function locals. 
That is, variables cannot shadow other variables from the same function. 
It allows shadowing of variables outside the function. This is 
deliberate. Otherwise, someone may name a variable somewhere else the 
same as yours, and your perfectly working code is now flagged as an error.

-Steve

Jun 23 2016

vladdeSV <v vladde.net> writes:

On Wednesday, 22 June 2016 at 12:47:31 UTC, TheDGuy wrote:
 On Wednesday, 22 June 2016 at 12:45:29 UTC, TheDGuy wrote:
 I have an array of buttons:

 class Window : MainWindow{
     private Button[4] bArr;
     this(){
         Button btn_1 = new Button();
         Button btn_2 = new Button();
         Button btn_3 = new Button();
         Button btn_4 = new Button();
         Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];
     }
     private void letButtonsFlash(){
         for(int i = 0; i < 4; i++){
             writeln(this.bArr[i].getName());
         }
     }
 }

 i don't understand why i get an 'Access Violation' - Error in 
 the 'for'-loop?

 Okay, i solved it, instead of:
 Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];

 this:
 bArr = [btn_1,btn_2,btn_3,btn_4];

I would also suggest you use a foreach loop to iterate over the 
buttons:

private void letButtonsFlash()
{
     foreach(button; bArr)
     {
         writeln(button.getName());
     }
}

//Also, question to anyone: should a ref be used here?

Jun 22 2016

Bell Baggins <Bell.Baggins skdjf.hu> writes:

On Wednesday, 22 June 2016 at 13:24:47 UTC, vladdeSV wrote:
 On Wednesday, 22 June 2016 at 12:47:31 UTC, TheDGuy wrote:
 On Wednesday, 22 June 2016 at 12:45:29 UTC, TheDGuy wrote:
 I have an array of buttons:

 class Window : MainWindow{
     private Button[4] bArr;
     this(){
         Button btn_1 = new Button();
         Button btn_2 = new Button();
         Button btn_3 = new Button();
         Button btn_4 = new Button();
         Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];
     }
     private void letButtonsFlash(){
         for(int i = 0; i < 4; i++){
             writeln(this.bArr[i].getName());
         }
     }
 }

 i don't understand why i get an 'Access Violation' - Error in 
 the 'for'-loop?

 Okay, i solved it, instead of:
 Button[4] bArr = [btn_1,btn_2,btn_3,btn_4];

 this:
 bArr = [btn_1,btn_2,btn_3,btn_4];

 I would also suggest you use a foreach loop to iterate over the 
 buttons:

 private void letButtonsFlash()
 {
     foreach(button; bArr)
     {
         writeln(button.getName());
     }
 }

 //Also, question to anyone: should a ref be used here?

No, ref for classes is pointless. The ptr destination is always 
the same heap chunk, whatever you use the original pointer or not.

Jun 22 2016

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