I tried to initialize an array of string in class as following:
class Haab{
string str[];
Haab(){
str[] = {"abc", "abd", "abe"};
}
};
But the Devc++ 5.6.1 reports a warning:
[Warning] extended initializer lists only available with -std=c++11 or -std=gnu++11 [enabled by default]
Is this way of initializing arrays in class illegal? If so, how to properly initialize the array? Thank you.
The given code,
class Haab{
string str[];
Haab(){
str[] = {"abc", "abd", "abe"};
}
};
is invalid in a number of ways:
string str[]; declares a member array of unknown size. Can't do that.
In str[] = {"abc", "abd", "abe"};, the expression str[] uses the [] indexing operator without specifying the index.
If that parsed, then the = would denote assignment of a single string.
Here's one C++03 way to do things:
#include <string>
#include <vector>
namespace qwe {
using std::string;
using std::vector;
class Haab
{
private:
vector<string> str_;
public:
Haab()
{
static char const* const data[] = {"abc", "abd", "abe"};
for( int i = 0; i < 3; ++i )
{
str_.push_back( data[i] );
}
}
};
} // namespace qwe
There are also other C++03 ways, all of them ugly (as the above).
In C++11 and later it can be done with more elegant & simple notation;
#include <string>
#include <vector>
namespace qwe {
using std::string;
using std::vector;
class Haab
{
private:
vector<string> str_;
public:
Haab()
: str_{ "abc", "abd", "abe"}
{}
};
} // namespace qwe
but this does still not compile with Visual C++ 13.0 (it does compile with MinGW g++ 4.9.1).
const they would have been equivalent. I use the syntax T const because that's the general syntax, e.g. it's what you have to use for the second const. But for the basic type of the declaration you can write const T for readability, and many prefer that even though it doesn't generalize; in particular it's done in all the standard's examples.
str[] = {"abc", "abd", "abe"};isn't even valid syntax as far as I know (separate from the declaration that is).char str[]in a struct, its probably a flexible array member (not valid in C++)