I have a class and function
class A
{
A(int i = 0)
{
}
}
void f(A a = new A(10)) // ? default parameter value must be compiler-time constanct
{
}
How to workaround it?
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If my answer below solved your issue please indicate so.Matt Rowland– Matt Rowland2016-05-15 23:24:58 +00:00Commented May 15, 2016 at 23:24
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1 Answer
You would need to do it inside the method and provide a comment that the method accepts null and uses A(10) as a default value.
void f(A a = null)
{
if(a == null)
a = new A(10);
}
6 Comments
Slugart
<cough> null coalescing operator </cough>
Matt Rowland
@Slugart That wouldn't work because the assignment only needs to be made if the object is
null. You could use a = a ?? new A(10); but there is no need.Slugart
?? is the null coalescing operator. There is no need but it is neater and more concise, right?
Matt Rowland
@Slugart If the parameter is not
null it will do the assignment still. It is an operation that doesn't need to happen. By doing the null check the assignment will only happen if a null is passed; or in this case by default.Slugart
Fortunately the c# and CLR teams thought of this and there's an IL instruction for it: stackoverflow.com/questions/13385503/…
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