digitalmars.D.learn - Nulling a reference to a class with opAssign ...
- Mike (19/19) Dec 07 2007 Erm ... this totally catched me off guard ...
- Steven Schveighoffer (26/26) Dec 07 2007 Your exact code compiles for me (dmd 1.0.23)... You sure you are using ...
- Mike (190/217) Dec 07 2007 On Fri, 07 Dec 2007 21:12:44 +0100, Steven Schveighoffer =
- Frank Benoit (2/2) Dec 07 2007 the best chance to get a good answer is, to provide a minimalistic and
- Mike (7/9) Dec 07 2007 The problem is that every minimalistic example compiles. I don't know.
- Mike (16/16) Dec 07 2007 On Fri, 07 Dec 2007 23:25:44 +0100, Frank Benoit =
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Jarrett Billingsley
(19/19)
Dec 07 2007
"Mike"
wrote in message news:op.t2zshuvdkgfkbn@lucia... - Mike (7/26) Dec 07 2007 .
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Jarrett Billingsley
(4/4)
Dec 07 2007
"Mike"
wrote in message news:op.t2zvuik9kgfkbn@lucia...
Erm ... this totally catched me off guard ... class Foo() { Bar barRef; ~this() { barRef.noMoreFoo(); } void opAssign(float f); } class Bar() { Foo fooRef; void setFoo(Foo foo) { fooRef =3D foo; } void noMoreFoo() { fooRef =3D null; } // error: can't cast void= * to = float ... } ? -Mike -- = Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
Dec 07 2007
Your exact code compiles for me (dmd 1.0.23)... You sure you are using the latest dmd? One observation, your destructor in Foo should not be accessing barRef because the garbage collector cannot guarantee that the barRef instance hasn't been collected. If you are in the destructor, there is no reason to clean up GC references anyways, as the GC will handle that. -Steve "Mike" wrote in message Erm ... this totally catched me off guard ... class Foo() { Bar barRef; ~this() { barRef.noMoreFoo(); } void opAssign(float f); } class Bar() { Foo fooRef; void setFoo(Foo foo) { fooRef = foo; } void noMoreFoo() { fooRef = null; } // error: can't cast void* to float ... } ? -Mike -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
Dec 07 2007
On Fri, 07 Dec 2007 21:12:44 +0100, Steven Schveighoffer = <schveiguy yahoo.com> wrote: DMD 1.023. Hmm. I've not tried the example before. Maybe it's because Foo and Bar a= re = actually template classes. Here's the actual code (yeah, I'm lazy with = comments and it's not yet finished). ----------------------------------------------------------------------- // test code void datacb(float value, uint id) { Stdout("datacb - val: ")(value)(" id: ")(id).newline; } void messagecb(EDBMessage msg, uint id) { Stdout("messagecb - id: ")(id).newline; } Stdout("testing databinding").newline; auto testsource =3D new CDataSource!(float); auto testsink1 =3D new CDataSink!(float)(testsource, &datacb, &messagecb= , 1); = testsource =3D 1.; ----------------------------------------------------------------------- // the actual code module tools.databinding; enum EDBMessage { sourceDeleted, sourceUpdated, } enum EDBForwardMode { push, poll, } enum EDBAccessMode { read, full, } class CDataSource(T) { public this(EDBForwardMode forward =3D EDBForwardMode.push, EDBAccessMo= de = access =3D EDBAccessMode.read) { myForwarding =3D forward; myAccess =3D access; } = public ~this() { // send every subscriber the deleted message foreach (item; mySubscribers) { if (item !is null) item.message(EDBMessage.sourceDeleted); } } = public void subscribe(CDataSink!(T) datasink) { // search if this sink is already subscribed foreach (item; mySubscribers) { if (item !is null && item is datasink) return; } = // search for a deleted subscriber foreach (item; mySubscribers) { if (item is null) { item =3D datasink; mySubscriberCount++; return; } } = // add at end of list mySubscribers ~=3D datasink; mySubscriberCount++; } = public void unSubscribe(CDataSink!(T) datasink) { foreach (item; mySubscribers) { if (item !is null && item is datasink) { item =3D null; mySubscriberCount--; return; } } } = public T opAssign(T value) { myValue =3D value; if (mySubscriberCount =3D=3D 0) return value; foreach (item; mySubscribers) { if (item !is null) { if (myForwarding =3D=3D EDBForwardMode.push) item.update(value); else item.message(EDBMessage.sourceUpdated); } } return myValue; } = public T opCall() { return myValue; } = public long subscriberCount() { return mySubscriberCount; } = private T myValue; private CDataSink!(T)[] mySubscribers; private long mySubscriberCount; private EDBForwardMode myForwarding; private EDBAccessMode myAccess; } class CDataSink(T) { public this(CDataSource!(T) source, void delegate(T, uint) valuecb, voi= d = delegate(EDBMessage, uint) messagecb, uint id) { myValueCallback =3D valuecb; myMessageCallback =3D messagecb; myId =3D id; subscribe(source); } = public ~this() { if (mySource !is null) mySource.unSubscribe(this); } = public void subscribe(CDataSource!(T) source) { if (mySource !is null) mySource.unSubscribe(this); if (source !is null) { mySource =3D source; mySource.subscribe(this); } } = public T opCall() { return mySource.myValue; } = public T opAssign(T value) { if (mySource.myAccess =3D=3D EDBAccessMode.full) return mySource =3D v= alue; throw new Exception("Databinding: Datasource is write protected."); } = public EDBForwardMode forwarding() { return mySource.myForwarding; } = public EDBAccessMode access() { return mySource.myAccess; } = private void update(T value) { if (myValueCallback !is null) myValueCallback(value, myId); } = private void message(EDBMessage message) { if (message =3D=3D EDBMessage.sourceDeleted) mySource =3D null; if (myMessageCallback !is null) myMessageCallback(message, myId); } = private CDataSource!(T) mySource; private void delegate(T, uint) myValueCallback; private void delegate(EDBMessage, uint) myMessageCallback; private uint myId; } ----------------------------------------------------------------------Your exact code compiles for me (dmd 1.0.23)... You sure you are usin=g =the latest dmd? One observation, your destructor in Foo should not be accessing barRef=because the garbage collector cannot guarantee that the barRef instanc=ehasn't been collected. If you are in the destructor, there is no reas=on =to clean up GC references anyways, as the GC will handle that. -Steve "Mike" wrote in message Erm ... this totally catched me off guard ... class Foo() { Bar barRef; ~this() { barRef.noMoreFoo(); } void opAssign(float f); } class Bar() { Foo fooRef; void setFoo(Foo foo) { fooRef =3D foo; } void noMoreFoo() { fooRef =3D null; } // error: can't cast vo=id* =to float ... } ? -Mike-- = Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
Dec 07 2007
the best chance to get a good answer is, to provide a minimalistic and tested example that shows your problem.
Dec 07 2007
On Fri, 07 Dec 2007 23:25:44 +0100, Frank Benoit <keinfarbton googlemail.com> wrote:the best chance to get a good answer is, to provide a minimalistic and tested example that shows your problem.The problem is that every minimalistic example compiles. I don't know. Maybe I'll spend some more time on that. But I figured out the solution anyway - I now just cast the null to the correct type and it works. -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
Dec 07 2007
On Fri, 07 Dec 2007 23:25:44 +0100, Frank Benoit = <keinfarbton googlemail.com> wrote: Ok ... got it: class Foo(T) { T opAssign(T v) { return v; } } void main() { auto foo =3D new Foo!(float)(); foo =3D cast(Foo!(float))null; // Works foo =3D null; // Error: Can't convert null to float } I'm not sure ... but I think the second assignment should work. -- = Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
Dec 07 2007
"Mike" <vertex gmx.at> wrote in message news:op.t2zshuvdkgfkbn lucia... On Fri, 07 Dec 2007 23:25:44 +0100, Frank Benoit <keinfarbton googlemail.com> wrote: ------------------- Ok ... got it: class Foo(T) { T opAssign(T v) { return v; } } void main() { auto foo = new Foo!(float)(); foo = cast(Foo!(float))null; // Works foo = null; // Error: Can't convert null to float } I'm not sure ... but I think the second assignment should work. ------------------- I absolutely think it should. It's checking for an opAssign, finding it, but not falling back to the default behavior.
Dec 07 2007
On Sat, 08 Dec 2007 03:13:34 +0100, Jarrett Billingsley = <kb3ctd2 yahoo.com> wrote:"Mike" <vertex gmx.at> wrote in message news:op.t2zshuvdkgfkbn lucia..=.On Fri, 07 Dec 2007 23:25:44 +0100, Frank Benoit <keinfarbton googlemail.com> wrote: ------------------- Ok ... got it: class Foo(T) { T opAssign(T v) { return v; } } void main() { auto foo =3D new Foo!(float)(); foo =3D cast(Foo!(float))null; // Works foo =3D null; // Error: Can't convert null to float } I'm not sure ... but I think the second assignment should work. ------------------- I absolutely think it should. It's checking for an opAssign, finding =it,but not falling back to the default behavior.Should I file it as a bug? -- = Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
Dec 07 2007
"Mike" <vertex gmx.at> wrote in message news:op.t2zvuik9kgfkbn lucia... Should I file it as a bug? -- Go ahead!
Dec 07 2007