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Why 'this' is a pointer and not a reference?
Why is this a pointer, rather rhan reference? Can it ever be NULL?
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It can be null. Imagine the case when a *non-virtual* method is invoked upon ... well, NULL :-) This might be well into the realm of C++ UB, but I've seen it occur before. – Nov 05 '10 at 04:59
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Exact duplicate of [Why 'this' is a pointer and not a reference?](http://stackoverflow.com/questions/645994/why-this-is-a-pointer-and-not-a-reference) and a handful of other questions. – James McNellis Nov 05 '10 at 05:03
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3@pst: Yes, that would be well into the realm of undefined behavior. – James McNellis Nov 05 '10 at 05:03
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1For one thing, it allows for `delete this;` – user229044 Nov 05 '10 at 05:04
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3@meagar: If it were a reference, you could `delete &this;`. – James McNellis Nov 05 '10 at 05:05
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@James Clearly the language was designed with `this` as a pointer solely to save one keystroke. Who wants to have to type `&this` *every time*? – user229044 Nov 05 '10 at 05:07
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@James McNellis - delete &this; might be tricky, if the class has overload for the operator &. – Franci Penov Nov 05 '10 at 05:08
2 Answers
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Why is "
this" not a reference?
See Bjarne's answer here
Because "this" was introduced into C++ (really into C with Classes) before references were added. Also, I chose "
this" to follow Simula usage, rather than the (later) Smalltalk use of "self".
Waqar
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Prasoon Saurav
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Why is
thisa pointer?
Because it is, and it is just the way the programming language was designed. (I think it is also because it was left over from C, but I am not sure).
rather than a reference?
If you need a this reference, use *this.
Can it never be
NULL?
...no. How could it be?
Cristian
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Alexander Rafferty
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2it's a reasonable question - if it can never be null or reassigned why isn't it a reference? – Martin Beckett Nov 05 '10 at 05:03
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why can't it be a pointer? There is no advantage of it being either because the conversion between involves one character (* or &). – Alexander Rafferty Nov 05 '10 at 05:13
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