EDIT: @stephentoub's proposal update from #1534 (comment) on 1/29/2022:
namespace System
{
public static class Nullable
{
+ public static ref readonly T GetValueRefOrDefaultRef<T>(in T? nullable) where T : struct => ref nullable.value;
}
}
Proposed API
namespace System
{
public static class Nullable
{
public static ref readonly T RefValue<T>(this in T? n) where T : struct;
public static ref readonly T RefValueOrDefault<T>(this in T? n) where T : struct;
public static ref readonly T RefValueOrDefault<T>(this in T? n, in T defaultValue) where T : struct;
}
}These parallel the Value property and the GetValueOrDefault methods of Nullable<T>, but return the value by reference. They're extension methods because of CS8170: Struct members cannot return 'this' or other instance members by reference.
They're useful for accessing the value wrapped by a Nullable<T> without incurring a copy.
Reference implementation
namespace System
{
public static class Nullable
{
public static ref readonly T RefValue<T>(this in T? n) where T : struct
{
if (n.HasValue)
return ref n.value;
else
throw new InvalidOperationException();
}
public static ref readonly T RefValueOrDefault<T>(this in T? n) where T : struct
{
return ref n.value;
}
public static ref readonly T RefValueOrDefault<T>(this in T? n, in T defaultValue) where T : struct
{
return ref n.HasValue ? ref n.value : ref defaultValue;
}
}
}
EDIT: @stephentoub's proposal update from #1534 (comment) on 1/29/2022:
namespace System { public static class Nullable { + public static ref readonly T GetValueRefOrDefaultRef<T>(in T? nullable) where T : struct => ref nullable.value; } }Proposed API
These parallel the Value property and the GetValueOrDefault methods of
Nullable<T>, but return the value by reference. They're extension methods because of CS8170: Struct members cannot return 'this' or other instance members by reference.They're useful for accessing the value wrapped by a
Nullable<T>without incurring a copy.Reference implementation