public ClassType(string type) {
Type = type;
}
public ClassType(string type,bool isArray=false) {
Type = type;
IsArray = isArray;
}
ClassType ct = new ClassType("adsf");
Which constructor is chosen?
views:
75answers:
2
+7
A:
The overload that doesn't require an optional parameter. Note that it's just a "yes" or "no" decision here: "no optional parameters filled in automatically" is preferable to "some optional parameters filled in automatically" but there's no preference between 1 or 2 being filled in. (That would be ambiguous.)
From section 7.5.3.2 of the C# 4 spec:
Otherwise if all parameters of MP have a corresponding argument whereas default arguments need to be substituted for at least one optional parameter in MQ then MP is better than MQ.
Jon Skeet
2010-07-13 12:41:45
Which raises the question, "Why isn't that a compile time error?" (I'm pretty sure it is in C++, and C# gives errors for a lot more edge cases that C++ lets by.)
James Curran
2010-07-13 14:10:56
@James: There's a method which exactly matches the arguments you've given, so I guess it's deemed to be fine. I suspect it makes it easier to add optional parameters to existing types.
Jon Skeet
2010-07-13 14:28:20
BTW: I've just ported that code to VC++ and confirmed that with that compiler at least, it is an error. I think the C++98 Standard makes it always an error. Odd that C# lets it pass. I guess it's to allow you to turn previously required parameters into optional params, but in that case you'd really want to know if you created an ambigity.
James Curran
2010-07-13 14:59:33