Re: Reserve vector with 100 strings each of fixed size 20
Diwa wrote:
I know I can reserve space for 100 strings in a vector by doing
following:
std::vector<std::string> m_vec;
m_vec.reserve(100)
But I also know that each of the string will be exactly 20 chars.
Can I use this fact while reserving the vector space above?
Not really.
'reserve' doesn't create any elements. It only allocates memory where
the elements will be later created, usually by means of 'placement new'.
If you need to create a vector of 100 strings, and each string to have
20 chars, you need to use 'resize' or construct it directly:
std::vector<std::string> m_vec;
... /* initializer list */ m_vec(100, std::string(20, 0)) ...
or
m_vec.resize(100, std::string(20, 0));
The reason for this most likely that 'std::string' has its own memory
management which isn't "activated" until the object is constructed.
And, as I mentioned, 'reserve' does not construct elements.
V
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