How to avoid variable capturing in `foreach` loop with lambdas?

[thebluepandabear]

I am using CSFML D bindings and I have created my own sort of UI 
library for drawing elements onto the screen.

One of the classes I've created is a `Button` class, which 
contains a delegate called `onButtonClick` which is called when 
the button is clicked on by the user.

Up until now, everything has worked fine.

I want to add a couple of buttons side by side to represent an 
element of a list and assign them each a unique lambda expression 
for that particular element in the list, this is the current code 
I have:

```D
foreach (BoardSize boardSize; arr) {
     Button button = new Button();
     button.text = format("%sx%s", boardSize[0], boardSize[1]);
     button.onButtonClick = {
         
eventHandler.settingsWindow_onBoardSizeButtonClick(boardSize);
     };
     button.onButtonClick();
     _boardSizeRow.addChild(button);
}
```

Running this code, I had expected that everything would work 
fine. Unfortunately upon running the code, tapping each of the 
buttons returned only the largest `boardSize` value, the one 
which is gets iterated last.

Note that I am still not totally sure why this is the case. At 
first, I was confused, but then I suspected that after the 
variable gets sent as a parameter to the 
`settingsWindow_onBoardSizeButtonClick` function, it gets changed 
again in the next iteration creating a sort of chain effect -- I 
may be wrong, but this is my suspicion.

Some of the things I tried was creating a new object each time, 
although it didn't work. I might have not done this properly as I 
am a beginner to D language. I saw someone else ask a similar 
question as to why this is happening but that was for C#, not D, 
so it wasn't that much of a use to me.

Help would be appreciated!