On Thursday, 5 January 2023 at 17:36:55 UTC, H. S. Teoh wrote:
On Thu, Jan 05, 2023 at 11:55:33AM +0000, thebluepandabear via
Digitalmars-d-learn wrote: [...]
```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);
}
```
This is a classic D trap: the loop variable is only allocated
once, and the closure captures the single location where the
loop variable resides, thus every delegate from every loop
iteration will see the same value when they are run later,
i.e., the last value of the loop index. Do this instead:
```D
foreach (BoardSize boardSize; arr) {
Button button = new Button();
button.text = format("%sx%s", boardSize[0], boardSize[1]);
BoardSize size = boardSize; // force separate capture
button.onButtonClick = {
eventHandler.settingsWindow_onBoardSizeButtonClick(size);
};
button.onButtonClick();
_boardSizeRow.addChild(button);
}
```
This is arguably a language bug (I can't imagine any sane use
case where somebody would actually want the current semantics).
But we have not be successful in convincing Walter about
this...
T
Your code with the variable capture doesn't seem to work.
