How does this statement works?

Question

I don't understand the syntax of this code:

private: System::Void entering_a_number(System::Object^ sender, System::EventArgs^ e) {
Button^ number_you_clicked = safe_cast<Button^>(sender); // this statement is so confusing to me, I read the document on MS site but still can not understand.

display->Text =
(
display->Text == "0"
) ?
number_you_clicked->Text
:
display->Text + number_you_clicked->Text;

}

If someone can explain this in simple english. Thank in advance.

Answer 1

Precaution:
I have no experience in Visual C++, so I will try to explain in general.

`entering_a_number` is a void function (returns nothing), it's an event handler that uses two arguments (`System::Object` <sender> and `System::EventArgs` <e>).

<sender> is an object that represents the UI control that triggers the event, <e> carries additional information regarding the event (usually be different for each event type).

Button^ number_you_clicked = safe_cast<Button^>(sender)

Means instantiate an object (a `Button` named <number_you_clicked>) that is generated by casting <sender> which is a general `System::Object` into a `Button` object (specific type).

The lines underneath shows a conditional execution flow through the use of ternary operator.

display->Text = (display->Text == "0")
? number_you_clicked->Text
: display->Text + number_you_clicked->Text;

If <display> text was "0", it will be updated to <number_you_clicked> text. Otherwise <number_you_clicked> text is appended to current text.

Hth, cmiiw