Is there a simple way to check if value is null for every case?

[rikki cattermole]

On 27/08/2018 12:51 PM, SG wrote:
> On Sunday, 26 August 2018 at 16:39:53 UTC, rikki cattermole wrote:
>> UFCS function called isNull.
>>
>> e.g.
>>
>> import std.traits : isPointer;
>> bool isNull(T)(T value) if (is(T == class) || isPointer!T) {
>>     return value is null;
>> }
> 
> Hi Rikki,
> 
> I'm still confused, I want to create a extension for checking null for 
> every type, so in D I'll need to handle each case with Templates?

Templates make it the easiest way, since common patterns, like arrays, 
classes and pointers have the exact same null check syntax.

> Because in C# I just need to compare an object/variable with null,
> 
> x == null;
> myObject == null;
> myObject.i == null;
> myStruct == null;
> myStruct.j == null;
> 
> This works fine in C#.

That code is only for classes. C# also has structs which are a value 
type. Which it would not work for.

> But again, in D I'll need the check the type? Is possible to make one 
> Template for all cases?
> 
> The code below works, but I don't think this is a right thing to do, right?

You don't need isNull function for Nullable because it has a method 
called it. That will be preferred (hence I specifically used isNull as 
the name).

For Variant, use hasValue.

bool isNull(Variant value) {
	return !value.hasValue;
}

Writing a Unified Function Call Syntax function isn't really an 
extension. You're defining a function that is to be preferred when you 
ask for a method of the same name. So that it appears as if it was 
actually described as a method instead of a free-function (not attached 
to class/interface/struct/union).