220 28976 article Path: news.gmane.org!.POSTED!not-for-mail From: Evan Teran Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: A means to access the encapsulating object within a member Date: Wed, 19 Oct 2016 08:02:07 -0700 (PDT) Lines: 120 Approved: news@gmane.org Message-ID: References: <4dffbd31-0ae3-4a10-9b57-f50f7e6aa8e7@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_217_1514164744.1476889327493" X-Trace: blaine.gmane.org 1476889351 31824 195.159.176.226 (19 Oct 2016 15:02:31 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 19 Oct 2016 15:02:31 +0000 (UTC) Cc: mihailnajdenov@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCDNZQVEQMLRB4MVT3AAKGQEL53XFCY@isocpp.org Wed Oct 19 17:02:23 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb0-f200.google.com ([209.85.213.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bwsNd-0005wU-V0 for gclcip-std-proposals@m.gmane.org; Wed, 19 Oct 2016 17:02:10 +0200 Original-Received: by mail-yb0-f200.google.com with SMTP id 206sf26317659ybp.4 for ; Wed, 19 Oct 2016 08:02:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=LdxTjafwCNT5ncUMJilWudqSxXi+tcbJ7snnm4a8JQg=; b=IwQu+w78NWlWY1QThavqJWnA4pp3VNl5pvcAVGCpIFxFxe8oOTmEzZ/FK13I8sV25h LNOODF9jtKhcVfiizHXOwVj2vubu+ew9kzz2yZfrpMSHY3v7xjfeVr/XX4cFNI4KqBPA umiQG5+BOhU6JT1vcGNK4+yTskoXmTxnbEH3SLkxVWyoX1XObvi+lkZ0OeNEL5quNTaC +p6kpbFKC969hP3i0Tlj86ZQy7KIJT2MSlWa+c/IecQ8Nn0nio/9BrC0x6ZR3QBIFrd4 3cM5/fuB1mh4JVir5u1lgC/3YCjpS3hN3hNARcegY/HX/tegOOOFsp6g6tjAjCWngdP2 31Yg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=LdxTjafwCNT5ncUMJilWudqSxXi+tcbJ7snnm4a8JQg=; b=pa2u6dpfOCJz2wBuNO11Ww4DfTyVjgmFg9rhoqJmZlhh7Mn8iKNMw+oWgGe5Rulb0K 6CaD02KIdNwDFODR61WnkH9oIGLTZdAb+W/XBaBVBT4nFi9GJJ8T+VX6qScK2Kx1lktr 2L3p9S2zgT+haw3+WawB5RXT9MeL4iQbv6J0YgWFA4Q0Ywfh7AcvLi8RarZi01JsHB09 ag7PMy9TcG9DtwSBEo68CbqLprRfA1ixep/sAq4ZPbD5bCq00Y3HF5U7aaikUU2W/9hc n5UNOIDm7xS5708J+X9s/lbXH4ZuWGlOQlctNS2BzRxIX0xmtz96QElQLhHVZDBbxdxl 60Ng== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:x-original-sender:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=LdxTjafwCNT5ncUMJilWudqSxXi+tcbJ7snnm4a8JQg=; b=W9KzWEBV3jqBJ97CLwk4GTVFLHpR4KRLa6fqiJsvnQySqaGZic6r5JVkjiCC5dAiFz pKClBK+WLK9qwZ11YiVtXF4q6+x+4t/PEkrnlUuLqCQRvio3WKlHciHdp0gAKD5L+yKD Frh7t3tH40Mbzu/MOZNSi5rkDyJajtJgTIr3AYsQNsNc68XfU9FF568gtrPX2NC16GdL RMHj/18FDrPZdg2pmLneWTtGzuBEFNNCP/ZXvLNg5044dkyrd3EDlvw90XRMXDQfFinV qYcszOJUsS3mIanQuEUzbZk/5HTFClMW3ad/bLHpyl0thVVSPNjahUKU19K9zlnAUboN K1Dw== X-Gm-Message-State: AA6/9RkdjRygsMWF0gFd/uvoqWWQx9XymVOFt2fbDedBfRoFiukgzRIgFOEvkplLQThvRw== X-Received: by 10.129.117.70 with SMTP id q67mr2057249ywc.45.1476889332054; Wed, 19 Oct 2016 08:02:12 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.11.69 with SMTP id v66ls733270ioi.37.gmail; Wed, 19 Oct 2016 08:02:09 -0700 (PDT) X-Received: by 10.36.124.22 with SMTP id a22mr638364itd.4.1476889329244; Wed, 19 Oct 2016 08:02:09 -0700 (PDT) In-Reply-To: X-Original-Sender: evan.teran@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:28976 Archived-At: ------=_Part_217_1514164744.1476889327493 Content-Type: multipart/alternative; boundary="----=_Part_218_749706940.1476889327493" ------=_Part_218_749706940.1476889327493 Content-Type: text/plain; charset=UTF-8 yes, you can store it via a constructor explicitly, I hadn't thought about using the in class version of the constructor which is nice. On Wednesday, October 19, 2016 at 5:44:00 AM UTC-4, mihailn...@gmail.com wrote: > > But you can always store a pointer in the contained class to the > containing class > > template > struct Property > { > Obj& operator=(const T &value) { > auto p = _that; > (p->*S)(value); > return *p; // we return the encapsulating object for intuitive > chaining > } > > operator T () const { > auto p = _that; > return (p->*G)(); > } > > Obj* _that; > }; > > > struct A { > > public: > int getMember() const { return member_; } // imagine that these are > complex routines > void setMember(int v) { member_ = v; } // and we couldn't get the > same behavior by making member_ public > > public: > Property member{this}; > > private: > int member_; > }; > > > This compiles and runs today. > > -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/cb8b588b-c265-416c-9b82-c074e28235d9%40isocpp.org. ------=_Part_218_749706940.1476889327493 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
yes, you can store it via a constructor explicitly, I hadn= 't thought about using the in class version of the constructor which is= nice.

On Wednesday, October 19, 2016 at 5:44:00 AM UTC-4, mihailn..= ..@gmail.com wrote:
But you can always store a pointer in the contained class to the = containing class

template <class T, class Obj, T (O= bj::*G)() const, void (Obj::*S)(T)>
struct Property=C2=A0
{
= =C2=A0=C2=A0=C2=A0 Obj& operator=3D(const T &value) {
=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 auto p =3D _that;
=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 (p->*S)(value);
=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 return *p; // we return the encapsulating object for intuit= ive chaining
=C2=A0=C2=A0=C2=A0 }
=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0= =C2=A0 operator T () const {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 = auto p =3D _that;
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return (p-&= gt;*G)();
=C2=A0=C2=A0=C2=A0 }
=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2= =A0 Obj* _that;
};


struct A {

public:
=C2=A0=C2=A0=C2=A0 int getM= ember() const { return member_; } // imagine that these are complex routine= s
=C2=A0=C2=A0=C2=A0 void setMember(int v) { member_ =3D v; }=C2=A0=C2= =A0=C2=A0 // and we couldn't get the same behavior by making member_ pu= blic

public:
=C2=A0=C2=A0=C2=A0 Property<int, A, &A::getMember, &= amp;A::setMember> member{this};
=C2=A0=C2=A0=C2=A0
private:
= =C2=A0=C2=A0=C2=A0 int member_;
};


This compil= es and runs today.

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To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/cb8b588b-c265-416c-9b82-c074e28235d9= %40isocpp.org.
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