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I've a constant struct timespec member in my class. How am I supposed to initialize it?
The only crazy idea I got is to derive my own timespec and give it a constructor.
Thanks much!
#include <iostream>
class Foo
{
private:
const timespec bar;
public:
Foo ( void ) : bar ( 1 , 1 )
{
}
};
int main() {
Foo foo;
return 0;
}
Compilation finished with errors: source.cpp: In constructor 'Foo::Foo()': source.cpp:9:36: error: no matching function for call to 'timespec::timespec(int, int)' source.cpp:9:36: note: candidates are: In file included from sched.h:34:0, from pthread.h:25, from /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../include/c++/4.7.2/i686-pc-linux-gnu/bits/gthr-default.h:41, from /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../include/c++/4.7.2/i686-pc-linux-gnu/bits/gthr.h:150, from /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../include/c++/4.7.2/ext/atomicity.h:34, from /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/ios_base.h:41, from /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../include/c++/4.7.2/ios:43, from /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../include/c++/4.7.2/ostream:40, from /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../include/c++/4.7.2/iostream:40, from source.cpp:1: time.h:120:8: note: timespec::timespec() time.h:120:8: note: candidate expects 0 arguments, 2 provided time.h:120:8: note: constexpr timespec::timespec(const timespec&) time.h:120:8: note: candidate expects 1 argument, 2 provided time.h:120:8: note: constexpr timespec::timespec(timespec&&) time.h:120:8: note: candidate expects 1 argument, 2 provided
311
To initialize the const value using constructor, we have to use the initialize list. This initializer list is used to initialize the data member of a class. The list of members, that will be initialized, will be present after the constructor after colon. members will be separated using comma.
Structure members cannot be initialized with declaration.
In C, we initialize or access a structure variable either through dot . or arrow -> operator. This is the most easiest way to initialize or access a structure.
Using designated initializers, a C99 feature which allows you to name members to be initialized, structure members can be initialized in any order, and any (single) member of a union can be initialized. Designated initializers are described in detail in Designated initializers for aggregate types (C only).
In C++11, you can initalise an aggregate member in the constructor's initialiser list:
Foo() : bar{1,1} {}
In older versions of the language, you would need a factory function:
Foo() : bar(make_bar()) {}
static timespec make_bar() {timespec bar = {1,1}; return bar;}
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