boost::bind with functions that have parameters that are references

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I noticed that when passing reference parameters to boost bind, those parameters won't act like references. Instead boost creates another copy of the member and the original passed in variable remains unchanged.

When I change the references to pointers, everything works ok.

My question is:

Is it possible to get references to work, or at least give a compiling error when it tries to use reference parameters?

c++ boost-bind

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edited Jul 11 '09 at 18:49 Piotr Dobrogost 14.7k981150

asked Jan 22 '09 at 17:19 Brian R. Bondy 145k60383516

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2 Answers

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up vote28down voteaccepted

The boost documentation for bind suggests that you can use boost::ref and boost::cref for this.

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edited Feb 8 '12 at 12:23 danio 3,02721635

answered Jan 22 '09 at 17:22 Timo Geusch 17k32449

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up vote2down vote

I ran into similar issue expecting a bind parameter to be passed by reference whenever the method used in the bind was declared to take a reference parameter. However this is NOT the case! You will need to explicitly wrap the bind parameter (that is to be passed by reference) in a boost::ref() or boost::cref() regardless of how the method is declared. Example: ClassA myClassAParameter void Method(ClassA &param); now, the following binding: callback = boost::bind(&Method, myClassAParameter); will actually make a COPY of the ClassA object (which i understand it is a temporary allocation and the called method should not keep a reference to it since this is not the reference of the actual object but to a copy of the object). however, the following binding: callback = boost::bind(&Method, boost::ref(myClassAParameter)); will not make a copy, but use a reference to create the bind object.

22down votefavorite

4

I noticed that when passing reference parameters to boost bind, those parameters won't act like references. Instead boost creates another copy of the member and the original passed in variable remains unchanged.

When I change the references to pointers, everything works ok.

My question is:

Is it possible to get references to work, or at least give a compiling error when it tries to use reference parameters?

c++ boost-bind

share|improve this question

edited Jul 11 '09 at 18:49 Piotr Dobrogost 14.7k981150

asked Jan 22 '09 at 17:19 Brian R. Bondy 145k60383516

add a comment

2 Answers

activeoldestvotes

up vote28down voteaccepted

The boost documentation for bind suggests that you can use boost::ref and boost::cref for this.

share|improve this answer

edited Feb 8 '12 at 12:23 danio 3,02721635

answered Jan 22 '09 at 17:22 Timo Geusch 17k32449

add a comment

up vote2down vote

I ran into similar issue expecting a bind parameter to be passed by reference whenever the method used in the bind was declared to take a reference parameter. However this is NOT the case! You will need to explicitly wrap the bind parameter (that is to be passed by reference) in a boost::ref() or boost::cref() regardless of how the method is declared. Example: ClassA myClassAParameter void Method(ClassA &param); now, the following binding: callback = boost::bind(&Method, myClassAParameter); will actually make a COPY of the ClassA object (which i understand it is a temporary allocation and the called method should not keep a reference to it since this is not the reference of the actual object but to a copy of the object). however, the following binding: callback = boost::bind(&Method, boost::ref(myClassAParameter)); will not make a copy, but use a reference to create the bind object.